Journal articles on the topic 'Skeletal muscle biopsy samples'
To see the other types of publications on this topic, follow the link: Skeletal muscle biopsy samples.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Skeletal muscle biopsy samples.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Kurt, YaseminGulcan, Bulent Kurt, Omer Ozcan, Turgut Topal, Abdullah Kilic, Tuba Muftuoglu, Cengizhan Acikel, et al. "Preservative solution for skeletal muscle biopsy samples." Annals of Indian Academy of Neurology 18, no. 2 (2015): 187. http://dx.doi.org/10.4103/0972-2327.150601.
Full text
2
Wendling, P. S., S. J. Peters, G. J. Heigenhauser, and L. L. Spriet. "Variability of triacylglycerol content in human skeletal muscle biopsy samples." Journal of Applied Physiology 81, no. 3 (September 1, 1996): 1150–55. http://dx.doi.org/10.1152/jappl.1996.81.3.1150.
Full textAbstract:
The variability of the triacylglycerol store in human skeletal muscle (TGm) was examined using the needle biopsy technique. In 13 subjects, three biopsies were sampled from the vastus lateralis muscle of one leg at rest and after 90 min of cycling at 65% of maximal O2 uptake on one or two occasions. Visible fat and blood were removed before the samples were frozen, and remaining blood, connective tissue, and fat were removed from freeze-dried fiber bundles. TGm content was measured in two aliquots of powdered muscle from each biopsy. Within-biopsy variability was low at 6%. Despite precautions, many biopsies from inactive subjects were contaminated with adipose tissue. The TGm between-biopsy coefficient of variation (CV) was 23.5 +/- 14.6% (SD, n = 24) for rest and exercise time points where three noncontaminated biopsies existed. The between-biopsy variability at rest (19.8 +/- 7.9%, n = 10) was not significantly different from that at exercise (26.1 +/- 17.4%, n = 14). The muscle glycogen between-biopsy CV for rest and exercise time points was 10.0 +/- 10.3%. The resting TGm content was 26.3 +/- 4.3 mmol/kg dry muscle, and the net utilization during the 90 min of exercise was less than the between-biopsy variability. It is concluded that the TGm store measured in repeated biopsies of human skeletal muscle is variable, with a CV of 20-26%. Therefore, because of this high variability, only changes greater than approximately 24% of resting TGm content may be considered meaningful.
3
Braga, Sérgio De Almeida, Felipe Gomes Ferreira Padilha, and Ana Maria Reis Ferreira. "Needle muscle biopsy: technique validation and histological and histochemical methods for evaluating canine skeletal muscles." Semina: Ciências Agrárias 38, no. 2 (May 2, 2017): 765. http://dx.doi.org/10.5433/1679-0359.2017v38n2p765.
Full textAbstract:
This study evaluated the needle muscle biopsy technique using a 6G Bergström percutaneous needle combined with histological and histochemical methods to analyze the skeletal muscle of dogs. There are few studies about canine skeletal muscles and a lack of reports in the literature about tissue collection and analysis for canine species. Evaluation of 32 German Shepherd samples collected from the gluteus medius, at a depth of 3 cm, was performed. The choice of gluteus medius and the 3-cm depth provided good quantity fragments with sufficient sizes (3–5 mm), which permitted optimal visualization of muscle fibers. Myosin ATPase, at pH 9.4, 4.6, and 4.3, and SDH reactions revealed that all muscle samples analyzed had fibers in the classic mosaic arrangement, enabling counting and typification. The mean percentages of fibers were 29.95% for type I and 70.05% for type II. On the basis of these results, we concluded that the percutaneous needle biopsy technique for canine skeletal muscles is a safe and easy procedure that obtains fragments of proper sizes, thereby enabling the study of muscle fibers. Standardization of the muscle of choice and the depth of muscle sample collection significantly contributed to this success. This is an important method to evaluate muscle fiber types of dogs and diagnose important diseases affecting the skeletal muscles.
4
Parker, Kenneth C., Ronan J. Walsh, Mohammad Salajegheh, Anthony A. Amato, Bryan Krastins, David A. Sarracino, and Steven A. Greenberg. "Characterization of Human Skeletal Muscle Biopsy Samples Using Shotgun Proteomics†." Journal of Proteome Research 8, no. 7 (July 6, 2009): 3265–77. http://dx.doi.org/10.1021/pr800873q.
Full text
5
Soderlund, K., and E. Hultman. "Effects of delayed freezing on content of phosphagens in human skeletal muscle biopsy samples." Journal of Applied Physiology 61, no. 3 (September 1, 1986): 832–35. http://dx.doi.org/10.1152/jappl.1986.61.3.832.
Full textAbstract:
The concentrations of ATP, phosphocreatine (PCr), creatine, and lactate were determined in muscle biopsy samples frozen immediately or after a delay of 1–6 min. During the delay the samples were exposed to normal air or a gas mixture of 6.5% CO2-93.5% O2. The ATP content was unchanged, but PCr increased significantly from 72 mmol after rapid freezing to 85 mmol X kg dry muscle-1 during the 1st min in air. The lactate concentration increased (2.8 to 5.2 mmol X kg-1). If muscles were made anoxic by circulatory occlusion for 4–6 min before sampling, no increase in PCr was observed. Direct homogenization of fresh tissue in perchloric acid gave the same ATP, PCr, and lactate contents as frozen samples. It is concluded that the ATP and PCr contents in muscle are unaffected by freezing but that the biopsy procedure activates the energy utilization processes resulting in PCr decrease. It is suggested that the muscle PCr content after a 1-min delay in tissue freezing corresponds to the level in resting fresh muscle.
6
Güttsches, Anne-Katrin, Robert Rehmann, Anja Schreiner, Marlena Rohm, Johannes Forsting, Martijn Froeling, Martin Tegenthoff, Matthias Vorgerd, and Lara Schlaffke. "Quantitative Muscle-MRI Correlates with Histopathology in Skeletal Muscle Biopsies." Journal of Neuromuscular Diseases 8, no. 4 (July 30, 2021): 669–78. http://dx.doi.org/10.3233/jnd-210641.
Full textAbstract:
Background: Skeletal muscle biopsy is one of the gold standards in the diagnostic workup of muscle disorders. By histopathologic analysis, characteristic features like inflammatory cellular infiltrations, fat and collagen replacement of muscle tissue or structural defects of the myofibers can be detected. In the past years, novel quantitative MRI (qMRI) techniques have been developed to quantify tissue parameters, thus providing a non-invasive diagnostic tool in several myopathies. Objective: This proof-of-principle study was performed to validate the qMRI-techniques to skeletal muscle biopsy results. Methods: Ten patients who underwent skeletal muscle biopsy for diagnostic purposes were examined by qMRI. Fat fraction, water T2-time and diffusion parameters were measured in the muscle from which the biopsy was taken. The proportion of fat tissue, the severity of degenerative and inflammatory parameters and the amount of type 1- and type 2- muscle fibers were determined in all biopsy samples. The qMRI-data were then correlated to the histopathological findings. Results: The amount of fat tissue in skeletal muscle biopsy correlated significantly with the fat fraction derived from the Dixon sequence. The water T2-time, a parameter for tissue edema, correlated with the amount of vacuolar changes of myofibers and endomysial macrophages in the histopathologic analysis. No significant correlations were found for diffusion parameters. Conclusion: In this proof-of-principle study, qMRI techniques were related to characteristic histopathologic features in neuromuscular disorders. The study provides the basis for further development of qMRI methods in the follow-up of patients with neuromuscular disorders, especially in the context of emerging treatment strategies.
7
Braund, K. G., and K. A. Amling. "Muscle Biopsy Samples for Histochemical Processing: Alterations Induced by Storage." Veterinary Pathology 25, no. 1 (January 1988): 77–82. http://dx.doi.org/10.1177/030098588802500111.
Full textAbstract:
Skeletal muscle samples from two healthy dogs were stored in ice at 0 C for up to 30 hours to examine the influence of time on cell morphology and morphometry. Cytochemical and histochemical properties of muscle to 18 hours were not markedly different from fresh frozen tissue. Samples stored to 30 hours were still satisfactory, despite a decline and unevenness in depth of staining. Morphometry from samples stored at 0 C for 6 hours or longer is not recommended, due to the statistically significant increase in diameter (from 21 to 25%) of type I and type II fibers.
8
Graham, T. E., B. Wolfe, and J. K. Barclay. "Active skeletal muscle metabolism and tension production: the influence of biopsies." Canadian Journal of Physiology and Pharmacology 71, no. 3-4 (March 1, 1993): 241–46. http://dx.doi.org/10.1139/y93-038.
Full textAbstract:
The influence of repeated sampling by the biopsy technique on skeletal muscle's metabolic and force-output responses was studied using the in situ canine gastrocnemius preparation. The left muscle was stimulated (8 V, 0.2 ms) for 1 h at 3 Hz. In the biopsy series (n = 9) muscle samples were taken at rest, and at 0.5, 2, 5, 15, 30, 45, and 60 min of stimulation. In the control series (n = 8) the left and right muscles were quick-frozen in N2 immediately after the 60 min of stimulation. The two series were not different in blood flow, [Formula: see text], arterial or venous [H+], muscle glycogen, or lactate release throughout the 60 min of activity. The lactate release was transient and was associated with an accumulation of intramuscular lactate and a period of rapid glycogenolysis. The biopsy series had a modest but significantly (p < 0.05) higher muscle lactate concentration both at rest and at the end of the contractions. The biopsy series also had less (p < 0.05) tension development throughout the hour; however, the O2 cost per unit of tension development was not different between groups, nor was the rate of tension decline over time different. This together with the similarities in perfusion, carbohydrate use, and lactate metabolism suggests that repeated biopsies had minimal impact on the muscle. The technique allows the collection of data over time; this improves the detail of experiments and means that fewer animals are required for a study.Key words: glycolysis, lactate, hydrogen ion, fatigue, muscle glycogen.
9
Constantin-Teodosiu, D., G. Cederblad, and E. Hultman. "PDC activity and acetyl group accumulation in skeletal muscle during isometric contraction." Journal of Applied Physiology 74, no. 4 (April 1, 1993): 1712–18. http://dx.doi.org/10.1152/jappl.1993.74.4.1712.
Full textAbstract:
The activity of pyruvate dehydrogenase complex (PDC) was studied in the human quadriceps femoris muscle during isometric contraction induced by intermittent electrical stimulation at 20 Hz. Muscle biopsy samples were obtained at rest and after 10, 20, and 46 contractions. The active form of PDC (PDCa) increased from a mean value of 26% of the total PDC at rest to mean values of 46, 78, and 80%, respectively. Muscle biopsy samples were also obtained at rest, after 46 contractions with limb blood flow intact or occluded, and after 2 min of oxidative recovery. In another experiment, muscle biopsy samples were obtained at rest, after 10 min of resting ischemia, and after 46 contractions with limb blood flow occluded. The transformation of PDC to PDCa was nearly complete, regardless of whether the blood flow was intact or occluded. However, the accumulation of acetyl groups observed during stimulation with intact blood flow was abolished when the blood flow was occluded. The absence of NADH oxidation during anoxia had no effect on the contraction-induced transformation of PDC to PDCa, but it inhibited the flux through the enzyme reaction.
10
Berthon, Phanélie M., Richard A. Howlett, George J. F. Heigenhauser, and Lawrence L. Spriet. "Human skeletal muscle carnitine palmitoyltransferase I activity determined in isolated intact mitochondria." Journal of Applied Physiology 85, no. 1 (July 1, 1998): 148–53. http://dx.doi.org/10.1152/jappl.1998.85.1.148.
Full textAbstract:
This study was designed to compare the activity of skeletal muscle carnitine palmitoyltransferase I (CPT I) in trained and inactive men ( n = 14) and women ( n = 12). CPT I activity was measured in intact mitochondria, isolated from needle biopsy vastus lateralis muscle samples (∼60 mg). The variability of CPT I activity determined on two biopsy samples from the same leg on the same day was 4.4, whereas it was 7.0% on two biopsy samples from the same leg on different days. The method was sensitive to the CPT I inhibitor malonyl-CoA (88% inhibition) and therefore specific for CPT I activity. The mean CPT I activity for all 26 subjects was 141.1 ± 10.6 μmol ⋅ min−1 ⋅ kg wet muscle (wm)−1 and was not different when all men vs. all women (140.5 ± 15.7 and 142.2 ± 14.5 μmol ⋅ min−1 ⋅ kg wm−1, respectively) were compared. However, CPT I activity was significantly higher in trained vs. inactive subjects for both men (176.2 ± 21.1 vs. 104.1 ± 13.6 μmol ⋅ min−1 ⋅ kg wm−1) and women (167.6 ± 14.1 vs. 91.2 ± 9.5 μmol ⋅ min−1 ⋅ kg wm−1). CPT I activity was also significantly correlated with citrate synthase activity (all subjects, r = 0.76) and maximal oxygen consumption expressed in milliliters per kilogram per minute (all subjects, r = 0.69). The results of this study suggest that CPT I activity can be accurately and reliably measured in intact mitochondria isolated from human muscle biopsy samples. CPT I activity was not affected by gender, and higher activities in aerobically trained subjects appeared to be the result of increased mitochondrial content in both men and women.
11
Troutman, Ashley D., Edgar J. Gallardo, Mary Beth Brown, and Andrew R. Coggan. "Measurement of nitrate and nitrite in biopsy-sized muscle samples using HPLC." Journal of Applied Physiology 125, no. 5 (November 1, 2018): 1475–81. http://dx.doi.org/10.1152/japplphysiol.00625.2018.
Full textAbstract:
Studies of rats have indicated that skeletal muscle plays a central role in whole-body nitrate ([Formula: see text])/nitrite ([Formula: see text])/nitric oxide (NO) metabolism. Extending these results to humans, however, is challenging due to the small size of needle biopsy samples. We therefore developed a method to precisely and accurately quantify [Formula: see text] and [Formula: see text] in biopsy-sized muscle samples. [Formula: see text] and [Formula: see text] were extracted from rat soleus samples using methanol combined with mechanical homogenization + ultrasound, bead beating, pulverization at liquid N2temperature or pulverization + 0.5% Triton X-100. After centrifugation to remove proteins, [Formula: see text] and [Formula: see text] were measured using HPLC. Mechanical homogenization + ultrasound resulted in the lowest [Formula: see text] content (62 ± 20 pmol/mg), with high variability [coefficient of variation (CV) >50%] across samples from the same muscle. The [Formula: see text]/[Formula: see text] ratio (0.019 ± 0.006) was also elevated, suggestive of [Formula: see text] reduction during tissue processing. Bead beating or pulverization yielded lower [Formula: see text] and slightly higher [Formula: see text] levels, but reproducibility was still poor. Pulverization + 0.5% Triton X-100 provided the highest [Formula: see text] content (124 ± 12 pmol/mg) and lowest [Formula: see text]/[Formula: see text] ratio (0.008 ± 0.001), with the least variability between duplicate samples (CV ~15%). These values are consistent with literature data from larger rat muscle samples analyzed using chemiluminescence. Samples were stable for at least 5 wk at −80°C, provided residual xanthine oxidoreductase activity was blocked using 0.1 mmol/l oxypurinol. We have developed a method capable of measuring [Formula: see text] and [Formula: see text] in <1 mg of muscle. This method should prove highly useful in investigating the role of skeletal muscle in [Formula: see text]/[Formula: see text]/NO metabolism in human health and disease.NEW & NOTEWORTHY Measurement of nitrate and especially nitrite in small, i.e., biopsy-sized, muscle samples is analytically challenging. We have developed a precise, accurate, and convenient method for doing so using an affordable commercial HPLC system.
12
Vandenborne, K., G. Walter, L. Ploutz-Snyder, R. Staron, A. Fry, K. De Meirleir, G. A. Dudley, and J. S. Leigh. "Energy-rich phosphates in slow and fast human skeletal muscle." American Journal of Physiology-Cell Physiology 268, no. 4 (April 1, 1995): C869—C876. http://dx.doi.org/10.1152/ajpcell.1995.268.4.c869.
Full textAbstract:
We investigated the relationship between energy-rich phosphate content and muscle fiber-type composition in human skeletal muscle using a combination of 31P-nuclear magnetic resonance spectroscopy (NMR), histochemical, and biochemical analyses of muscle biopsies. Localized 31P spectra were collected simultaneously from the predominantly slow-twitch soleus muscle and the mixed (fast-twitch and slow-twitch) medial and lateral gastrocnemius muscles, using B1-insensitive Hadamard Spectroscopic Imaging. Biopsy samples were taken from the soleus and lateral gastrocnemius muscles before NMR investigation and analyzed for fiber type composition and succinic dehydrogenase (SDH) activity. Fiber-type composition was determined based both on myofibrillar actomyosin ATPase activity combined with cross-sectional area and on myosin heavy-chain composition. Localized spectroscopy demonstrated a significantly (P < 0.001) higher P(i)/phosphocreatine ratio in the soleus muscle (0.15 +/- 0.01) compared with the medial (0.12 +/- 0.01) and lateral (0.10 +/- 0.0) gastrocnemius. However, in vitro analysis of muscle biopsies showed only a moderate relationship between the basal phosphate content and myofibrillar actomyosin ATPase-based fiber-type composition and SDH activity, respectively.
13
Biereder, S., M. Wicke, G. von Lengerken, F. Schneider, and W. Kanitz. "Muskelwachstum und IGF-I bei Schweinen unterschiedlichen Geschlechts*." Archives Animal Breeding 42, no. 6 (October 10, 1999): 619–28. http://dx.doi.org/10.5194/aab-42-619-1999.
Full textAbstract:
Abstract. Title ofthe paper: Growth of skeletal muscle and IGF-I in pigs of different sex IGF-I is a pluripotent factor that is involved in regulation of growth, differentiation and a large number of functions in numerous tissues and their cells. IGF-I is synthesized by hepatocytes (endocrine role) and several extrahepatic tissues (e.g. skeletal muscle; autoerine and paracrine role). In our study, we describe the postnatal growth of the skeletal muscles in pigs of various sex taking into account the possible influence of endogenous IGF-I. The investigation was made on 42 crossbred pigs. Seven blood samples and 4 biopsy samples of two muscles (M. longissimus dorsi and M. triceps brachii) were taken for the determination of IGF-I blood plasma concentration and muscle fibre diameter, respectively as well as for further muscle structural and biochemical traits. IGF-I plasma concentrations show an increase during fattening with significantly highest levels for boars. Phenotypic differences between sows and boars in thickness of Shoulder muscle are proven after the day 181 with ultrasonography because significant differences were detected in mean muscle area of caput longum musculi triceps brachii between sows and boars and barrows (180th day of life). There are no significant differences in mean muscle fibre diameter of both muscles between sexes. A group of animals with high mean diameter in muscle fibres (day 200) of M. triceps brachii has significantly higher IGF-I concentrations in blood plasma than a group of animals with low muscle fibre diameter in the same muscle.
14
Liggett, S. B., S. D. Shah, and P. E. Cryer. "Characterization of beta-adrenergic receptors of human skeletal muscle obtained by needle biopsy." American Journal of Physiology-Endocrinology and Metabolism 254, no. 6 (June 1, 1988): E795—E798. http://dx.doi.org/10.1152/ajpendo.1988.254.6.e795.
Full textAbstract:
Human skeletal muscle beta-adrenergic receptors were characterized by 125I-iodopindolol radioligand-binding studies of homogenates prepared from small muscle samples obtained by percutaneous needle biopsy from the gastrocnemius of six normal subjects. Binding was saturable, reversible, and stereospecific, with typical kinetics and a rank-order potency characteristic of a beta-adrenergic receptor. In saturation-binding studies, the receptor density was 9.7 +/- 1.9 fmol/mg protein, with a dissociation constant of 24 +/- 2.2 pM. Competition studies with selective antagonists revealed a population of receptors exclusively of the beta 2-subtype. Basal and isoproterenol-stimulated adenylate cyclase activities were 79 +/- 22 and 150 +/- 60 pmol adenosine 3',5'-cyclic monophosphate.min-1.mg protein-1, respectively. These results support pharmacological observations of beta-adrenergic receptor-mediated cellular responses in mammalian skeletal muscle. By use of these methods, small quantities of skeletal muscle obtained in this manner can be used to study in vivo beta-adrenergic receptor regulatory phenomena in humans.
15
Watt, Matthew J., George J. F. Heigenhauser, and Lawrence L. Spriet. "Intramuscular triacylglycerol utilization in human skeletal muscle during exercise: is there a controversy?" Journal of Applied Physiology 93, no. 4 (October 1, 2002): 1185–95. http://dx.doi.org/10.1152/japplphysiol.00197.2002.
Full textAbstract:
Intramuscular triacylglyerols (IMTGs) represent a potentially important energy source for contracting human skeletal muscle. Although the majority of evidence from isotope tracer and 1H-magnetic resonance spectroscopy (MRS) studies demonstrate IMTG utilization during exercise, controversy regarding the importance of IMTG as a metabolic substrate persists. The controversy stems from studies that measure IMTG in skeletal muscle biopsy samples and report no significant net IMTG degradation during prolonged moderate-intensity (55–70% maximal O2 consumption) exercise lasting 90–120 min. Although postexercise decrements in IMTG levels are often reported from direct muscle measurements, the marked between-biopsy variability (∼23%) that has been reported with this technique in untrained subjects is larger than the expected decrease in IMTG content, effectively precluding significant findings. In contrast, recent data obtained in endurance-trained subjects demonstrated reduced variability between duplicate biopsies (∼12%), and significant changes in IMTG were detected after 120 min of moderate-intensity exercise. Therefore, it is our contention that the muscle biopsy, isotope tracer, and 1H-MRS techniques report significant and energetically important oxidation of free fatty acids derived from IMTGs during prolonged moderate exercise.
16
Sycheva, A. M., V. D. Nazarova, S. V. Lapin, M. G. Rybakova, and D. I. Rudenko. "Optimization of the pre-analytical stage of material processing for histochemical examination of skeletal muscle biopsies in the diagnosis of neuromuscular diseases." Neuromuscular Diseases 9, no. 2 (July 14, 2019): 21–29. http://dx.doi.org/10.17650/2222-8721-2019-9-2-21-29.
Full textAbstract:
Diagnosis of neuromuscular diseases is complicated by the variety of clinical manifestations and requires the use of additional methods, an important place among which is the pathomorphological study of skeletal muscle biopsy. Despite the fact that the procedure for taking a muscle biopsy is not technically difficult, to obtain informative material a multitude of conditions must be observed at the stages of pre-analytical processing of the obtained tissue samples. Violation of the technology of taking, storing and fixing the material contributes to the formation of artifacts that limit the possibilities for further analysis of the morphological changes in tissue biopsy. A comparison was made of the effectiveness of various methods for cryoprocessing of muscle tissue samples and the manufacture of histological specimens with a subsequent assessment of morphological changes. As a result, the main causes of artifacts were identified. The optimal method for processing muscle biopsy specimens is indicated, which makes it possible to prevent the appearance of artifacts as much as possible and to ensure the preservation of tissue for research.
17
WAGENMAKERS, ANTON J. M., and RICHARD H. T. EDWARDS. "Tissue-effective investigation of mitochondrial metabolism in needle biopsy samples of human skeletal muscle." Biochemical Society Transactions 14, no. 4 (August 1, 1986): 696–97. http://dx.doi.org/10.1042/bst0140696.
Full text
18
Dmitrieva, R. I., T. A. Lelyavina, M. Y. Komarova, V. L. Galenko, O. A. Ivanova, P. A. Tikanova, N. V. Khromova, et al. "Skeletal Muscle Resident Progenitor Cells Coexpress Mesenchymal and Myogenic Markers and Are Not Affected by Chronic Heart Failure-Induced Dysregulations." Stem Cells International 2019 (January 3, 2019): 1–11. http://dx.doi.org/10.1155/2019/5690345.
Full textAbstract:
Background and Purpose. In heart failure (HF), metabolic alterations induce skeletal muscle wasting and decrease of exercise capacity and quality of life. The activation of skeletal muscle regeneration potential is a prospective strategy to reduce muscle wasting; therefore, the aim of this project was to determine if functional properties of skeletal muscle mesenchymal progenitor cells (SM-MPC) were affected by HF-induced functional and metabolic dysregulations. Methods. Gastrocnemius muscle biopsy samples were obtained from 3 healthy donors (HD) and 12 HF patients to purify mRNA for further analysis and to isolate SM-MPC. Cells were expanded in vitro and characterized by immunocytochemistry and flow cytometry for expression of mesenchymal (CD105/CD73/CD166/CD146/CD140b/CD140a/VIM) and myogenic (Myf5/CD56/MyoG) markers. Cells were induced to differentiate and were then analyzed by immunostaining and Q-PCR to verify the efficiency of differentiation. The expression of genes that control muscle metabolism and development was compared for HD/HF patients in both muscle biopsy and in vitro-differentiated myotubes. Results. The upregulation of MYH3/MYH8/Myf6 detected in HF skeletal muscle along with metabolic alterations indicates chronic pathological activation of the muscle developmental program. SM-MPC isolated from HD and HF patients represented a mixed population that coexpresses both mesenchymal and myogenic markers and differs from AD-MMSC, BM-MMSC, and IMF-MSC. The functional properties of SM-MPC did not differ between HD and HF patients. Conclusion. In the present work, we demonstrate that the metabolic and functional alterations we detected in skeletal muscle from HF patients do not dramatically affect the functional properties of purified and expanded in vitro SM-MPC. We speculate that skeletal muscle progenitor cells are protected by their niche and under beneficial circumstances could contribute to muscle restoration and prevention and treatment of muscle wasting. The potential new therapeutic strategies of HF-induced skeletal muscle wasting should be targeted on both activation of SM-MPC regeneration potential and improvement of skeletal muscle metabolic status to provide a favorable environment for SM-MPC-driven muscle restoration.
19
Drummond, Micah J., Kyle L. Timmerman, Melissa M. Markofski, Dillon K. Walker, Jared M. Dickinson, Mohammad Jamaluddin, Allan R. Brasier, Blake B. Rasmussen, and Elena Volpi. "Short-term bed rest increases TLR4 and IL-6 expression in skeletal muscle of older adults." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 305, no. 3 (August 1, 2013): R216—R223. http://dx.doi.org/10.1152/ajpregu.00072.2013.
Full textAbstract:
Bed rest induces significant loss of leg lean mass in older adults. Systemic and tissue inflammation also accelerates skeletal muscle loss, but it is unknown whether inflammation is associated to inactivity-induced muscle atrophy in healthy older adults. We determined if short-term bed rest increases toll-like receptor 4 (TLR4) signaling and pro-inflammatory markers in older adult skeletal muscle biopsy samples. Six healthy, older adults underwent seven consecutive days of bed rest. Muscle biopsies (vastus lateralis) were taken after an overnight fast before and at the end of bed rest. Serum cytokine expression was measured before and during bed rest. TLR4 signaling and cytokine mRNAs associated with pro- and anti-inflammation and anabolism were measured in muscle biopsy samples using Western blot analysis and qPCR. Participants lost ∼4% leg lean mass with bed rest. We found that after bed rest, muscle levels of TLR4 protein expression and interleukin-6 (IL-6), nuclear factor-κB1, interleukin-10, and 15 mRNA expression were increased after bed rest ( P < 0.05). Additionally, the cytokines interferon-γ, and macrophage inflammatory protein-1β, were elevated in serum samples following bed rest ( P < 0.05). We conclude that short-term bed rest in older adults modestly increased some pro- and anti-inflammatory cytokines in muscle samples while systemic changes in pro-inflammatory cytokines were mostly absent. Upregulation of TLR4 protein content suggests that bed rest in older adults increases the capacity to mount an exaggerated, and perhaps unnecessary, inflammatory response in the presence of specific TLR4 ligands, e.g., during acute illness.
20
Fagher, Birger, Hans Liedholm, Mario Monti, and Ulrich Moritz. "Thermogenesis in human skeletal muscle as measured by direct microcalorimetry and muscle contractile performance during β-adrenoceptor blockade." Clinical Science 70, no. 5 (May 1, 1986): 435–41. http://dx.doi.org/10.1042/cs0700435.
Full textAbstract:
1. The influence of β-adrenoceptor-blockade on skeletal muscle was studied in ten healthy males with propranolol, atenolol and pindolol randomly given for 8 days each in a cross-over double blind test. After 7 days on each drug, muscle function was tested by an isokinetic dynamometer. Thermogenesis in biopsy samples taken from vastus lateralis muscle after a low grade exercise was studied after 8 days on each drug by direct calorimetry with a perfusion microcalorimeter. 2. Before drug administration, a median heat production rate of 0.67 mW/g of muscle was measured. This value was significantly reduced by 25% during propranolol, but no significant change was found during atenolol or pindolol administration. 3. Peak torque decline during isokinetic endurance test changed significantly in knee flexor but not in extensor muscles, from 15% to 27% after propranolol and from 15% to 23% after pindolol. Maximum dynamic strength was unaltered. 4. Our data suggest that blockade of sympathetic β2-receptors decreases thermogenesis in human skeletal muscle and impairs isokinetic endurance.
21
Kanaley, Jill A., Samyah Shadid, Michael T. Sheehan, ZengKui Guo, and Michael D. Jensen. "Hyperinsulinemia and skeletal muscle fatty acid trafficking." American Journal of Physiology-Endocrinology and Metabolism 305, no. 4 (August 15, 2013): E540—E548. http://dx.doi.org/10.1152/ajpendo.00143.2013.
Full textAbstract:
We hypothesized that insulin alters plasma free fatty acid (FFA) trafficking into intramyocellular (im) long-chain acylcarnitines (imLCAC) and triglycerides (imTG). Overnight-fasted adults ( n = 41) received intravenous infusions of [U-13C]palmitate (0400–0900 h) and [U-13C]oleate (0800–1400 h) to label imTG and imLCAC. A euglycemic-hyperinsulinemic (1.0 mU·kg fat-free mass−1·min−1) clamp (0800–1400 h) and two muscle biopsies (0900 h, 1400 h) were performed. The patterns of [U-13C]palmitate incorporation into imTG-palmitate and palmitoylcarnitine were similar to those we reported in overnight postabsorptive adults (saline control); the intramyocellular palmitoylcarnitine enrichment was not different from and correlated with imTG-palmitate enrichment for both the morning ( r = 0.38, P = 0.02) and afternoon ( r = 0.44, P = 0.006) biopsy samples. Plasma FFA concentrations, flux, and the incorporation of plasma oleate into imTG-oleate during hyperinsulinemia were ∼1/10th of that observed in the previous saline control studies ( P < 0.001). At the time of the second biopsy, the enrichment in oleoylcarnitine was <25% of that in imTG-oleate and was not correlated with imTG-oleate enrichment. The intramyocellular nonesterified fatty acid-palmitate-to-imTG-palmitate enrichment ratio was greater ( P < 0.05) in women than men, suggesting that sex differences in intramyocellular palmitate trafficking may occur under hyperinsulinemic conditions. We conclude that plasma FFA trafficking into imTG during hyperinsulinemia is markedly suppressed, and these newly incorporated FFA fatty acids do not readily enter the LCAC preoxidative pools. Hyperinsulinemia does not seem to inhibit the entry of fatty acids from imTG pools that were labeled under fasting conditions, possibly reflecting the presence of two distinct imTG pools that are differentially regulated by insulin.
22
McGuire, B. J., and T. W. Secomb. "Estimation of capillary density in human skeletal muscle based on maximal oxygen consumption rates." American Journal of Physiology-Heart and Circulatory Physiology 285, no. 6 (December 2003): H2382—H2391. http://dx.doi.org/10.1152/ajpheart.00559.2003.
Full textAbstract:
A previously developed Krogh-type theoretical model was used to estimate capillary density in human skeletal muscle based on published measurements of oxygen consumption, arterial partial pressure of oxygen, and blood flow during maximal exercise. The model assumes that oxygen consumption in maximal exercise is limited by the ability of capillaries to deliver oxygen to tissue and is therefore strongly dependent on capillary density, defined as the number of capillaries per unit cross-sectional area of muscle. Based on an analysis of oxygen transport processes occurring at the microvascular level, the model allows estimation of the minimum number of straight, evenly spaced capillaries required to achieve a given oxygen consumption rate. Estimated capillary density values were determined from measurements of maximal oxygen consumption during knee extensor exercise and during whole body cycling, and they range from 459 to 1,468 capillaries/mm2. Measured capillary densities, obtained with either histochemical staining techniques or electron microscopy on quadriceps muscle biopsies from healthy subjects, are generally lower, ranging from 123 to 515 capillaries/mm2. This discrepancy is partly accounted for by the fact that capillary density decreases with muscle contraction and muscle biopsy samples typically are strongly contracted. The results imply that estimates of maximal oxygen transport rates based on capillary density values obtained from biopsy samples do not fully reflect the oxygen transport capacity of the capillaries in skeletal muscle.
23
Adachi, Susumu, Hiroshi Ito, Mimi Tamamori, Masato Tanaka, Fumiaki Marumo, and Michiaki Hiroe. "Skeletal and smooth muscle α-actin mRNA in endomyocardial biopsy samples of dilated cardiomyopathy patients." Life Sciences 63, no. 20 (October 1998): 1779–91. http://dx.doi.org/10.1016/s0024-3205(98)00452-4.
Full text
24
Mahoney, D. J., A. Safdar, G. Parise, S. Melov, Minghua Fu, L. MacNeil, J. Kaczor, E. T. Payne, and M. A. Tarnopolsky. "Gene expression profiling in human skeletal muscle during recovery from eccentric exercise." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 294, no. 6 (June 2008): R1901—R1910. http://dx.doi.org/10.1152/ajpregu.00847.2007.
Full textAbstract:
We used cDNA microarrays to screen for differentially expressed genes during recovery from exercise-induced muscle damage in humans. Male subjects ( n = 4) performed 300 maximal eccentric contractions, and skeletal muscle biopsy samples were analyzed at 3 h and 48 h after exercise. In total, 113 genes increased 3 h postexercise, and 34 decreased. At 48 h postexercise, 59 genes increased and 29 decreased. On the basis of these data, we chose 19 gene changes and conducted secondary analyses using real-time RT-PCR from muscle biopsy samples taken from 11 additional subjects who performed an identical bout of exercise. Real-time RT-PCR analyses confirmed that exercise-induced muscle damage led to a rapid (3 h) increase in sterol response element binding protein 2 ( SREBP-2), followed by a delayed (48 h) increase in the SREBP-2 gene targets Acyl CoA:cholesterol acyltransferase ( ACAT)-2 and insulin-induced gene 1 ( insig-1). The expression of the IL-1 receptor, a known regulator of SREBP-2, was also elevated after exercise. Taken together, these expression changes suggest a transcriptional program for increasing cholesterol and lipid synthesis and/or modification. Additionally, damaging exercise induced the expression of protein kinase H11, capping protein Z alpha ( capZα), and modulatory calcineurin-interacting protein 1 ( MCIP1), as well as cardiac ankryin repeat protein 1 ( CARP1), DNAJB2, c-myc, and junD, each of which are likely involved in skeletal muscle growth, remodeling, and stress management. In summary, using DNA microarrays and RT-PCR, we have identified novel genes that respond to skeletal muscle damage, which, given the known biological functions, are likely involved in recovery from and/or adaptation to damaging exercise.
25
Mannion, A. F., P. M. Jakeman, and P. L. Willan. "Determination of human skeletal muscle buffer value by homogenate technique: methods of measurement." Journal of Applied Physiology 75, no. 3 (September 1, 1993): 1412–18. http://dx.doi.org/10.1152/jappl.1993.75.3.1412.
Full textAbstract:
The human muscle buffer value (beta) is most frequently determined by either fixed acid titration of a homogenate ["in vitro" beta (beta vit)] or measurement of the change in lactate concentration (delta [La]) relative to the change in muscle homogenate pH after high-intensity exercise ["in vitro" beta = - delta [La]/delta pH (beta viv)]. We sought to compare beta viv, determined after isometric and dynamic exercise to exhaustion (approximately 60 s), with beta vit. Resting (R) and postexercise (E) biopsy samples were taken from vastus lateralis muscles of 43 human volunteers. Freeze-dried muscle was homogenized (30 mg/ml) in NaF (0.01 M) for the measurement of muscle pH (R and E). beta vit was determined by HCl (0.01 M) titration of the homogenate over the pH range 7.1–6.5. Muscle lactate was measured by enzymatic assay. There was no significant difference between beta viv determined after isometric (n = 35) or dynamic (n = 8) exercise to fatigue (170 vs. 168 mmol H+.kg dry muscle mass-1.pH-1, respectively; P > 0.05). Values for beta vit in the corresponding muscle samples (R) were approximately 7–8% lower (156 +/- 25 vs. 157 +/- 18 mmol H+.kg dry muscle mass-1.pH-1, respectively). There was no significant difference (P = 0.278) between the measured decline in muscle homogenate pH after exercise and the reduction in pH predicted from beta vit and delta [La], indirectly confirming the lack of any significant difference between beta viv and beta vit.(ABSTRACT TRUNCATED AT 250 WORDS)
26
Houmard, J. A., M. S. Hickey, G. L. Tyndall, K. E. Gavigan, and G. L. Dohm. "Seven days of exercise increase GLUT-4 protein content in human skeletal muscle." Journal of Applied Physiology 79, no. 6 (December 1, 1995): 1936–38. http://dx.doi.org/10.1152/jappl.1995.79.6.1936.
Full textAbstract:
Insulin-responsive glucose transporter (GLUT-4) content increases by 1.8-fold in skeletal muscle with 14 wk of exercise training [Houmard et al. Am. J. Physiol. 264 (Endocrinol. Metab. 27): E896-E901, 1993]. The purpose of this study was to determine whether more short-term training (7 days) increases GLUT-4 protein content in human skeletal muscle. Seven sedentary men [25.0 +/- 1.1 (SE) yr, 44.1 +/- 2.2 ml.kg-1.min-1 maximal O2 uptake, 14.9 +/- 2.1% body fat] were examined before and after 7 days of cycle ergometer training (1 h/day, 76 +/- 2% maximal heart rate). Needle biopsy samples from the vastus lateralis were used to determine GLUT-4 protein content. Muscle GLUT-4 increased (P < 0.05) by an average of 2.8 +/- 0.5-fold with 7 days of training. GLUT-4 content in skeletal muscle thus increases substantially with short-term exercise training.
27
Freund, Daniel, Silke Brilloff, Tamer Ghazy, Stephan Kirschner, Gabor Gäbel, Irene Hinterseher, Norbert Weiss, and Adrian Mahlmann. "Microarray analysis for delineating the gene expression in biopsies of gastrocnemius muscle of patients with chronic critical limb ischaemia compared with non-ischaemic controls." Vasa 47, no. 4 (June 1, 2018): 295–300. http://dx.doi.org/10.1024/0301-1526/a000700.
Full textAbstract:
Abstract. Background: Microarray analysis has been carried out in this pilot study to compare delineated gene expression profiles in the biopsies of skeletal muscle taken from patients with chronic critical limb ischaemia (CLI) and non-ischaemic control subjects. Patients and methods: Biopsy of gastrocnemius muscle was obtained from six patients with unreconstructed CLI referred for surgical major amputation. As control, biopsies of six patients undergoing elective knee arthroplasty without evidence of peripheral arterial occlusive disease were taken. The differences in gene expression associated with angiogenic processes in specimens obtained from ischaemic and non-ischaemic skeletal muscle were confirmed by quantitative real-time polymerase chain reaction (PCR) analysis. Results: Compared with non-ischaemic skeletal muscle biopsy of chronic-ischaemic skeletal muscle contained 55 significantly up-regulated and 45 down-regulated genes, out of which 64 genes had a known genetic product. Tissue samples of ischaemic muscle were characterized by increased expression of cell survival factors (e. g. tissue factor pathway inhibitor 2) in combination with reduced expression of cell proliferation effectors (e. g. microfibrillar-associated protein 5 and transferrin receptor). The expression of growth factors (e. g. early growth response 3 and chemokine receptor chemokine C-X-C motif ligand 4) which play a central role in arterial and angiogenic processes and anti-angiogenetic factors (e. g. pentraxin 3) were increased in chronic ischaemic skeletal muscle. An increased expression of extracellular matrix proteins (e. g. cysteine-rich angiogenic inducer 61) was also observed. Conclusions: Gene expression profiles in biopsies of gastrocnemius muscle in patients with chronic critical limb ischaemia showed an increase in pro-survival factors, extracellular matrix protein deposition, and impaired proliferation, compared with non-ischaemic controls. Further studies are required to analyse the endogenous repair mechanism.
28
Bonen, A., K. J. A. McCullagh, C. T. Putman, E. Hultman, N. L. Jones, and G. J. F. Heigenhauser. "Short-term training increases human muscle MCT1 and femoral venous lactate in relation to muscle lactate." American Journal of Physiology-Endocrinology and Metabolism 274, no. 1 (January 1, 1998): E102—E107. http://dx.doi.org/10.1152/ajpendo.1998.274.1.e102.
Full textAbstract:
We examined the effects of increasing a known lactate transporter protein, monocarboxylate transporter 1 (MCT1), on lactate extrusion from human skeletal muscle during exercise. Before and after short-term bicycle ergometry training [2 h/day, 7 days at 65% maximal oxygen consumption (V˙o 2 max)], subjects ( n = 7) completed a continuous bicycle ergometer ride at 30%V˙o 2 max (15 min), 60%V˙o 2 max (15 min), and 75% V˙o 2 max (15 min). Muscle biopsy samples (vastus lateralis) and arterial and femoral venous blood samples were obtained before exercise and at the end of each workload. After 7 days of training the MCT1 content in muscle was increased (+18%; P < 0.05). The concentrations of both muscle lactate and femoral venous lactate were reduced during exercise ( P < 0.05) that was performed after training. High correlations were observed between muscle lactate and venous lactate before training ( r = 0.92, P < 0.05) and after training ( r = 0.85, P < 0.05), but the slopes of the regression lines between these variables differed markedly. Before training, the slope was 0.12 ± 0.01 mM lactate ⋅ mmol lactate−1 ⋅ kg muscle dry wt−1, and this was increased by 33% after training to 0.18 ± 0.02 mM lactate ⋅ mmol lactate−1 ⋅ kg muscle dry wt−1. This indicated that after training the femoral venous lactate concentrations were increased for a given amount of muscle lactate. These results suggest that lactate extrusion from exercising muscles is increased after training, and this may be associated with the increase in skeletal muscle MCT1.
29
Lednev, E. M., V. E. Dubrov, and D. V. Popov. "Use of branched-chain amino acids for reducing exercise-caused skeletal muscle damage." Innovative Medicine of Kuban, no. 3 (September 21, 2022): 13–19. http://dx.doi.org/10.35401/2541-9897-2022-25-3-13-19.
Full textAbstract:
Introduction: Skeletal muscles damage (direct and vicarious) slows down the recovery processes in patients with injuries of the musculoskeletal system. It occurs in the early postoperative period as well. An increase in the rigidity of the skeletal muscle extracellular matrix can reduce pain, tissue swelling, and accelerate the recovery of contractility.Objective: The analyses of the effect of branched-chain amino acids (BCAAs) intake on the expression of IGF1 genes, type 1, 3 and 5 collagen, which are crucial in the composition of the skeletal muscle extracellular matrix, as well as on the muscle membrane damage against the background of chronic damage to skeletal muscles.Material and methods: 12 young healthy male subjects, skiers aged 19 (18; 22) received a placebo treatment (maltodextrin, 100 mg/kg body weight/day; n = 6) or a mixture of amino acids (leucine, isoleucine, valine – 50:25:20 mg/kg body weight/day respectively; n = 6). The treatment was received daily against the background of a large amount of aerobic high-intensity training (up to 22 hours per week). Before and after the amino acids intake a biopsy of the musculus vastus lateralis was performed, and venous blood samples were taken during the experiment.Results: The intake of leucine against the background of training led not only to a pronounced increase in the level of IGF1 protein in blood by 1.5 times (which corresponds to the literature data), but also to a trend towards an increase in the expression of IGF1Ea mRNA by 1.8 times in the skeletal muscle, and a decrease in the level of markers of muscle membranes damage – creatine phosphokinase (CPK) activity and myoglobin. In addition, changes in the IGF1-dependent collagen genes expression strongly correlated with changes in IGF1Ea expression, but not with IGF1 protein in blood (pooled group, n = 12). Thus, the intake of leucine as a part of the essential amino acids can reduce damage to skeletal muscles caused by excessive physical activity, lack of physical activity, or direct trauma.Conclusion: A 10-week BCAAs intake by individuals with documented chronic muscle membrane damage caused an increase of basal levels of IGF1 in blood and a trend towards increased IGF1Ea mRNA expression in skeletal muscle, and also caused a modest reduction in damage of skeletal muscle membrane.
30
Jacobs, Robert A., Anne-Kristine Meinild, Nikolai B. Nordsborg, and Carsten Lundby. "Lactate oxidation in human skeletal muscle mitochondria." American Journal of Physiology-Endocrinology and Metabolism 304, no. 7 (April 1, 2013): E686—E694. http://dx.doi.org/10.1152/ajpendo.00476.2012.
Full textAbstract:
Lactate is an important intermediate metabolite in human bioenergetics and is oxidized in many different tissues including the heart, brain, kidney, adipose tissue, liver, and skeletal muscle. The mechanism(s) explaining the metabolism of lactate in these tissues, however, remains unclear. Here, we analyze the ability of skeletal muscle to respire lactate by using an in situ mitochondrial preparation that leaves the native tubular reticulum and subcellular interactions of the organelle unaltered. Skeletal muscle biopsies were obtained from vastus lateralis muscle in 16 human subjects. Samples were chemically permeabilized with saponin, which selectively perforates the sarcolemma and facilitates the loss of cytosolic content without altering mitochondrial membranes, structure, and subcellular interactions. High-resolution respirometry was performed on permeabilized muscle biopsy preparations. By use of four separate and specific substrate titration protocols, the respirometric analysis revealed that mitochondria were capable of oxidizing lactate in the absence of exogenous LDH. The titration of lactate and NAD+ into the respiration medium stimulated respiration ( P ≤ 0.003). The addition of exogenous LDH failed to increase lactate-stimulated respiration ( P = 1.0). The results further demonstrate that human skeletal muscle mitochondria cannot directly oxidize lactate within the mitochondrial matrix. Alternately, these data support previous claims that lactate is converted to pyruvate within the mitochondrial intermembrane space with the pyruvate subsequently taken into the mitochondrial matrix where it enters the TCA cycle and is ultimately oxidized.
31
Caiozzo, V. J., F. Haddad, S. Lee, M. Baker, William Paloski, and K. M. Baldwin. "Artificial gravity as a countermeasure to microgravity: a pilot study examining the effects on knee extensor and plantar flexor muscle groups." Journal of Applied Physiology 107, no. 1 (July 2009): 39–46. http://dx.doi.org/10.1152/japplphysiol.91130.2008.
Full textAbstract:
The goal of this project was to examine the effects of artificial gravity (AG) on skeletal muscle strength and key anabolic/catabolic markers known to regulate muscle mass. Two groups of subjects were selected for study: 1) a 21 day-bed rest (BR) group ( n = 7) and 2) an AG group ( n = 8), which was subjected to 21 days of 6° head-down tilt bed rest plus daily 1-h exposures to AG (2.5 G at the feet). Centrifugation was produced using a short-arm centrifuge with the foot plate ∼220 cm from the center of rotation. The torque-velocity relationships of the knee extensors and plantar flexors of the ankle were determined pre- and posttreatment. Muscle biopsy samples obtained from the vastus lateralis and soleus muscles were used for a series of gene expression analyses (mRNA abundance) of key factors implicated in the anabolic vs. catabolic state of the muscle. Post/pre torque-velocity determinations revealed greater decrements in knee extensor performance in the BR vs. AG group ( P < 0.04). The plantar flexors of the AG subjects actually demonstrated a net gain in the torque-velocity relationship, whereas in the BR group, the responses declined (AG vs. BR, P < 0.001). Muscle fiber cross-sectional area decreased by ∼20% in the BR group, whereas no losses were evident in the AG group. RT-PCR analyses of muscle biopsy specimens demonstrated that markers of growth and cytoskeletal integrity were higher in the AG group, whereas catabolic markers were elevated in the BR group. Importantly, these patterns were seen in both muscles. We conclude that paradigms of AG have the potential to maintain the functional, biochemical, and structural homeostasis of skeletal muscle in the face of chronic unloading.
32
Alsted, Thomas J., Lars Nybo, Martina Schweiger, Christian Fledelius, Poul Jacobsen, Robert Zimmermann, Rudolf Zechner, and Bente Kiens. "Adipose triglyceride lipase in human skeletal muscle is upregulated by exercise training." American Journal of Physiology-Endocrinology and Metabolism 296, no. 3 (March 2009): E445—E453. http://dx.doi.org/10.1152/ajpendo.90912.2008.
Full textAbstract:
Mobilization of fatty acids from stored triacylglycerol (TG) in adipose tissue and skeletal muscle [intramyocellular triacylglycerol (IMTG)] requires activity of lipases. Although exercise training increases the lipolytic capacity of skeletal muscle, the expression of hormone-sensitive lipase (HSL) is not changed. Recently, adipose triglyceride lipase (ATGL) was identified as a TG-specific lipase in various rodent tissues. To investigate whether human skeletal muscle ATGL protein is regulated by endurance exercise training, 10 healthy young men completed 8 wk of supervised endurance exercise training. Western blotting analysis on lysates of skeletal muscle biopsy samples revealed that exercise training induced a twofold increase in skeletal muscle ATGL protein content. In contrast to ATGL, expression of comparative gene identification 58 (CGI-58), the activating protein of ATGL, and HSL protein was not significantly changed after the training period. The IMTG concentration was significantly decreased by 28% at termination of the training program compared with before. HSL-phoshorylation at Ser660 was increased, HSL-Ser659 phosporylation was unchanged, and HSL-phoshorylation at Ser565 was decreased altogether, indicating an enhanced basal activity of this lipase. No change was found in the expression of diacylglycerol acyl transferase 1 (DGAT1) after training. Inhibition of HSL with a monospecific, small molecule inhibitor (76-0079) and stimulation of ATGL with CGI-58 revealed that significant ATGL activity is present in human skeletal muscle. These results suggest that ATGL in addition to HSL may be important for human skeletal muscle lipolysis.
33
Lee-Young, Robert S., Benedict J. Canny, Damian E. Myers, and Glenn K. McConell. "AMPK activation is fiber type specific in human skeletal muscle: effects of exercise and short-term exercise training." Journal of Applied Physiology 107, no. 1 (July 2009): 283–89. http://dx.doi.org/10.1152/japplphysiol.91208.2008.
Full textAbstract:
AMP-activated protein kinase (AMPK) has been extensively studied in whole muscle biopsy samples of humans, yet the fiber type-specific expression and/or activation of AMPK is unknown. We examined basal and exercise AMPK-α Thr172 phosphorylation and AMPK subunit expression (α1, α2, and γ3) in type I, IIa, and IIx fibers of human skeletal muscle before and after 10 days of exercise training. Before training basal AMPK phosphorylation was greatest in type IIa fibers ( P < 0.05 vs. type I and IIx), while an acute bout of exercise increased AMPK phosphorylation in all fibers ( P < 0.05), with the greatest increase occurring in type IIx fibers. Exercise training significantly increased basal AMPK phosphorylation in all fibers, and the exercise-induced increases were uniformly suppressed compared with pretraining exercise. Expression of AMPK-α1 and -α2 was similar between fibers and was not altered by exercise training. However, AMPK-γ3 was differentially expressed in skeletal muscle fibers (type IIx > type IIa > type I), irrespective of training status. Thus skeletal muscle AMPK phosphorylation and AMPK expression are fiber type specific in humans in the basal state, as well as during exercise. Our findings reveal fiber type-specific differences that have been masked in previous studies examining mixed muscle samples.
34
Lebeck, Janne, Esben Søndergaard, and Søren Nielsen. "Increased AQP7 abundance in skeletal muscle from obese men with type 2 diabetes." American Journal of Physiology-Endocrinology and Metabolism 315, no. 3 (September 1, 2018): E367—E373. http://dx.doi.org/10.1152/ajpendo.00468.2017.
Full textAbstract:
Aquaglyceroporin 7 (AQP7) facilitates the transport of glycerol across cell membranes. In mice, fasting and refeeding regulate adipose tissue AQP7 abundance, and a role in controlling triglyceride accumulation in adipose tissue has been proposed. AQP7 is also expressed in skeletal muscle, where its function remains to be determined. Here, the abundance of AQP7 in abdominal subcutaneous adipose tissue (SAT) and skeletal muscle was evaluated in the overnight fasted and postprandial state in eight lean and eight obese men with type 2 diabetes (T2D). A biopsy from SAT and muscle was collected after an overnight fast and 2 h after ingestion of a low-fat test meal. Palmitate turnover was evaluated using a [9,10-3H] palmitate dilution technique. Tissue samples were analyzed by immunoblotting. Meal intake did not affect AQP7 expression in SAT or skeletal muscle. No association between the SAT AQP7 abundance and palmitate turnover was found. SAT AQP7 abundance was similar in lean and obese T2D men, whereas muscle AQP7 abundance was more than fourfold higher in obese T2D men. In conclusion, meal intake did not affect AQP7 protein abundance in SAT or skeletal muscle. In addition, SAT AQP7 expression does not appear to be involved in the regulation of adipose tissue lipolysis. However, in contrast to SAT AQP7, skeletal muscle AQP7 protein abundance is markedly increased in obese T2D men, potentially contributing to the excess lipid accumulation in skeletal muscle in type 2 diabetes.
35
Mccall, Gary E., William C. Byrnes, Arthur L. Dickinson, and Steven J. Fleck. "Sample Size Required for the Accurate Determination of Fiber Area and Capillarity of Human Skeletal Muscle." Canadian Journal of Applied Physiology 23, no. 6 (December 1, 1998): 594–99. http://dx.doi.org/10.1139/h98-034.
Full textAbstract:
This study aimed to determine the skeletal muscle fiber sample size required for a reliable, valid representation of an individual's average fiber area and capillary contacts (CC) per fiber. Biopsies were obtained from the biceps brachii of 11 college-age, recreational resistance-trained men in conjunction with a study investigating how muscle morphology changed after 12 weeks of resistance training. The effect of additional measurements on the rolling cumulative means for fiber area and CC per fiber was evaluated using sequential estimation analysis. Results showed that group cumulative mean and standard deviation had stabilized by 50 fiber measurements per individual for type I and II fibers and CC per fiber. Significant correlations (.96-.99; p < .05) existed between the 50th and 95th/100th cumulative individual means. These results indicate that a typical skeletal muscle needle biopsy would be sufficient to characterize type I and II fiber areas and CC per fiber of an individual in most subject populations, although the required sample size for characterizing fiber subtypes might be different. Key words: muscle biopsy; sequential estimation analysis
36
Begue, Gwénaëlle, Ulrika Raue, Bozena Jemiolo, and Scott Trappe. "DNA methylation assessment from human slow- and fast-twitch skeletal muscle fibers." Journal of Applied Physiology 122, no. 4 (April 1, 2017): 952–67. http://dx.doi.org/10.1152/japplphysiol.00867.2016.
Full textAbstract:
A new application of the reduced representation bisulfite sequencing method was developed using low-DNA input to investigate the epigenetic profile of human slow- and fast-twitch skeletal muscle fibers. Successful library construction was completed with as little as 15 ng of DNA, and high-quality sequencing data were obtained with 32 ng of DNA. Analysis identified 143,160 differentially methylated CpG sites across 14,046 genes. In both fiber types, selected genes predominantly expressed in slow or fast fibers were hypomethylated, which was supported by the RNA-sequencing analysis. These are the first fiber type-specific methylation data from human skeletal muscle and provide a unique platform for future research. NEW & NOTEWORTHY This study validates a low-DNA input reduced representation bisulfite sequencing method for human muscle biopsy samples to investigate the methylation patterns at a fiber type-specific level. These are the first fiber type-specific methylation data reported from human skeletal muscle and thus provide initial insight into basal state differences in myosin heavy chain I and IIa muscle fibers among young, healthy men.
37
Yarar-Fisher, Ceren, C. Scott Bickel, Neil A. Kelly, Michael J. Stec, Samuel T. Windham, Amie B. McLain, Robert A. Oster, and Marcas M. Bamman. "Heightened TWEAK-NF-κB signaling and inflammation-associated fibrosis in paralyzed muscles of men with chronic spinal cord injury." American Journal of Physiology-Endocrinology and Metabolism 310, no. 9 (May 1, 2016): E754—E761. http://dx.doi.org/10.1152/ajpendo.00240.2015.
Full textAbstract:
Individuals with long-standing spinal cord injury (SCI) often present with extreme muscle atrophy and impaired glucose metabolism at both the skeletal muscle and whole body level. Persistent inflammation and increased levels of proinflammatory cytokines in the skeletal muscle are potential contributors to dysregulation of glucose metabolism and atrophy; however, to date no study has assessed the effects of long-standing SCI on their expression or intracellular signaling in the paralyzed muscle. In the present study, we assessed the expression of genes (TNFαR, TNFα, IL-6R, IL-6, TWEAK, TWEAK R, atrogin-1, and MuRF1) and abundance of intracellular signaling proteins (TWEAK, TWEAK R, NF-κB, and p-p65/p-50/105) that are known to mediate inflammation and atrophy in skeletal muscle. In addition, based on the effects of muscle inflammation on promotion of skeletal muscle fibrosis, we assessed the degree of fibrosis between myofibers and fascicles in both groups. For further insight into the distribution and variability of muscle fiber size, we also analyzed the frequency distribution of SCI fiber size. Resting vastus lateralis (VL) muscle biopsy samples were taken from 11 men with long-standing SCI (≈22 yr) and compared with VL samples from 11 able-bodied men of similar age. Our results demonstrated that chronic SCI muscle has heightened TNFαR and TWEAK R gene expression and NF-κB signaling (higher TWEAK R and phospho-NF-κB p65) and fibrosis, along with substantial myofiber size heterogeneity, compared with able-bodied individuals. Our data suggest that the TWEAK/TWEAK R/NF-κB signaling pathway may be an important mediator of chronic inflammation and fibrotic adaptation in SCI muscle.
38
Hedges, C. P., J. S. T. Woodhead, H. W. Wang, C. J. Mitchell, D. Cameron-Smith, A. J. R. Hickey, and T. L. Merry. "Peripheral blood mononuclear cells do not reflect skeletal muscle mitochondrial function or adaptation to high-intensity interval training in healthy young men." Journal of Applied Physiology 126, no. 2 (February 1, 2019): 454–61. http://dx.doi.org/10.1152/japplphysiol.00777.2018.
Full textAbstract:
Measurement of skeletal muscle mitochondrial respiration requires invasive biopsy to obtain a muscle sample. Peripheral blood mononuclear cell (PBMC) mitochondrial protein content appears to reflect training status in young men; however, no studies have investigated whether there are training-induced changes in PBMC mitochondrial respiration. Therefore, we determined whether PBMC mitochondrial respiration could be used as a marker of skeletal muscle mitochondrial respiration in young healthy men and whether PBMC mitochondrial respiration responds to short-term training. Skeletal muscle and PBMC samples from 10 healthy young (18–35 yr) male participants were taken before and after a 2-wk high-intensity interval training protocol. High-resolution respirometry was used to determine mitochondrial respiration from muscle and PBMCs, and Western blotting and quantitative PCR were used to assess mitochondrial biogenesis in PBMCs. PBMC mitochondrial respiration was not correlated with muscle mitochondrial respiration at baseline ( R2 = 0.012–0.364, P > 0.05). While muscle mitochondrial respiration increased in response to training (32.1–61.5%, P < 0.05), PBMC respiration was not affected by training. Consequently, PBMCs did not predict training effect on muscle mitochondrial respiration ( R2 = 0.024–0.283, P > 0.05). Similarly, gene and protein markers of mitochondrial biogenesis did not increase in PBMCs following training. This suggests PBMC mitochondrial function does not reflect that of skeletal muscle and does not increase following short-term high-intensity training. PBMCs are therefore not a suitable biomarker for muscle mitochondrial function in young healthy men. It may be useful to study PBMC mitochondrial function as a biomarker of muscle mitochondrial function in pathological populations with different respiration capacities. NEW & NOTEWORTHY Research in primates has suggested that peripheral blood mononuclear cells (PBMCs) may provide a less-invasive alternative to a muscle biopsy for measuring muscle mitochondrial function. Furthermore, trained individuals appear to have greater mitochondrial content in PBMCs. Here we show that in healthy young men, PBMCs do not reflect skeletal muscle mitochondrial function and do not adapt in response to a training intervention that increases muscle mitochondrial function, suggesting PBMCs are a poor marker of muscle mitochondrial function in humans.
39
Goldsmith, Rochelle, Denis R. Joanisse, Dympna Gallagher, Katherine Pavlovich, Elisabeth Shamoon, Rudolph L. Leibel, and Michael Rosenbaum. "Effects of experimental weight perturbation on skeletal muscle work efficiency, fuel utilization, and biochemistry in human subjects." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 298, no. 1 (January 2010): R79—R88. http://dx.doi.org/10.1152/ajpregu.00053.2009.
Full textAbstract:
Maintenance of a body weight 10% above or below that “customary” for lean or obese individuals results in respective increases or decreases in the energy expended in low levels of physical activity (nonresting energy expenditure, NREE). These changes are greater than can be accounted for by the altered body weight or composition and are due mainly to altered skeletal muscle work efficiency at low levels of power generation. We performed biochemical analysis of vastus lateralis muscle needle biopsy samples to determine whether maintenance of an altered body weight was associated with changes in skeletal muscle histomorphology. We found that the maintenance of a 10% reduced body weight was associated with significant declines in glycolytic (phosphofructokinase, PFK) enzyme activity and, in particular, in the ratio of glycolytic to oxidative (cytochrome c oxidase, COX) enzyme activity without significant changes in the activities of enzymes relevant to mitochondrial density, respiratory chain activity, or fuel transport; or in skeletal muscle fiber type or glycogen stores. The fractional change in the ratio of PFK/COX activity in subjects following weight loss was significantly correlated with changes in the systemic respiratory exchange ratio (RER) and measures of mechanical efficiency of skeletal muscle at low workloads (pedaling a bicycle to generate 10 or 25 W of power). Thus, predictable changes in systemic skeletal muscle biochemistry accompany the maintenance of an altered body weight and account for a significant portion of the variance in skeletal muscle work efficiency and fuel utilization at reduced body weight.
40
Polasek, L. K., K. A. Dickson, and R. W. Davis. "Metabolic indicators in the skeletal muscles of harbor seals (Phoca vitulina)." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 290, no. 6 (June 2006): R1720—R1727. http://dx.doi.org/10.1152/ajpregu.00080.2005.
Full textAbstract:
The goal of this study was to determine the distribution of citrate synthase (CS), β-hydroxyacyl coenzyme A dehydrogenase (HOAD), and lactate dehydrogenase (LDH) activities and myoglobin (Mb) concentration in the locomotor muscles (epaxial muscles) and heart of harbor seals. The entire epaxial musculature, which produces most of the power for submerged swimming, was removed and weighed, and three transverse sections (cranial, middle, and caudal) were taken along the muscle bundle. Multiple samples were taken along points on a circular grid using a 6-mm biopsy. A single sample was taken from the left ventricle of the heart. Muscle groups of similar function were taken from three dogs as a control. Mean values were calculated for four roughly equal quadrants in each transverse section of the epaxial muscles. There were no significant differences among the quadrants within any of the transverse sections for the three enzymes or Mb. However, there were significant differences in the mean enzyme activities and Mb concentrations along the length of the muscle. The middle and caudal sections had significantly higher mean levels of CS, LDH, and Mb than the cranial section, which may be correlated with power production during swimming. The enzyme ratios CS/HOAD and LDH/CS exhibited no variation within transverse sections or along the length of the epaxial muscles. Relative to the dog, the epaxial muscles and heart of the harbor seal had higher HOAD levels and lower CS/HOAD, which, taken together, indicate an increased capacity for aerobic lipid metabolism during diving.
41
Febbraio, Mark A., and Jane Dancey. "Skeletal muscle energy metabolism during prolonged, fatiguing exercise." Journal of Applied Physiology 87, no. 6 (December 1, 1999): 2341–47. http://dx.doi.org/10.1152/jappl.1999.87.6.2341.
Full textAbstract:
A depletion of phosphocreatine (PCr), fall in the total adenine nucleotide pool (TAN = ATP + ADP + AMP), and increase in TAN degradation products inosine 5′-monophosphate (IMP) and hypoxanthine are observed at fatigue during prolonged exercise at 70% maximal O2 uptake in untrained subjects [J. Baldwin, R. J. Snow, M. F. Carey, and M. A. Febbraio. Am. J. Physiol. 277 ( Regulatory Integrative Comp. Physiol.46): R295–R300, 1999]. The present study aimed to examine whether these metabolic changes are also prevalent when exercise is performed below the blood lactate threshold (LT). Six healthy, untrained humans exercised on a cycle ergometer to voluntary exhaustion at an intensity equivalent to 93 ± 3% of LT (∼65% peak O2 uptake). Muscle biopsy samples were obtained at rest, at 10 min of exercise, ∼40 min before fatigue (F−40 =143 ± 13 min), and at fatigue (F = 186 ± 31 min). Glycogen concentration progressively declined ( P < 0.01) to very low levels at fatigue (28 ± 6 mmol glucosyl U/kg dry wt). Despite this, PCr content was not different when F−40 was compared with F and was only reduced by 40% when F was compared with rest (52.8 ± 3.7 vs. 87.8 ± 2.0 mmol/kg dry wt; P < 0.01). In addition, TAN concentration was not reduced, IMP did not increase significantly throughout exercise, and hypoxanthine was not detected in any muscle samples. A significant correlation ( r = 0.95; P < 0.05) was observed between exercise time and glycogen use, indicating that glycogen availability is a limiting factor during prolonged exercise below LT. However, because TAN was not reduced, PCr was not depleted, and no correlation was observed between glycogen content and IMP when glycogen stores were compromised, fatigue may be related to processes other than those involved in muscle high-energy phosphagen metabolism.
42
Louche, Katie, Pierre-Marie Badin, Emilie Montastier, Claire Laurens, Virginie Bourlier, Isabelle de Glisezinski, Claire Thalamas, Nathalie Viguerie, Dominique Langin, and Cedric Moro. "Endurance Exercise Training Up-Regulates Lipolytic Proteins and Reduces Triglyceride Content in Skeletal Muscle of Obese Subjects." Journal of Clinical Endocrinology & Metabolism 98, no. 12 (December 1, 2013): 4863–71. http://dx.doi.org/10.1210/jc.2013-2058.
Full textAbstract:
Context: Skeletal muscle lipase and intramyocellular triglyceride (IMTG) play a role in obesity-related metabolic disorders. Objectives: The aim of the present study was to investigate the impact of 8 weeks of endurance exercise training on IMTG content and lipolytic proteins in obese male subjects. Design and Volunteers: Ten obese subjects completed an 8-week supervised endurance exercise training intervention in which vastus lateralis muscle biopsy samples were collected before and after training. Main Outcome Measures: Clinical characteristics and ex vivo substrate oxidation rates were measured pre- and posttraining. Skeletal muscle lipid content and lipolytic protein expression were also investigated. Results: Our data show that exercise training reduced IMTG content by 42% (P < .01) and increased skeletal muscle oxidative capacity, whereas no change in total diacylglycerol content and glucose oxidation was found. Exercise training up-regulated adipose triglyceride lipase, perilipin (PLIN) 3 protein, and PLIN5 protein contents in skeletal muscle despite no change in mRNA levels. Training also increased hormone sensitive–lipase Ser660 phosphorylation. No significant changes in comparative gene identification 58, G0/G1 switch gene 2, and PLIN2 protein and mRNA levels were observed in response to training. Interestingly, we noted a strong relationship between skeletal muscle comparative gene identification 58 and mitochondrial respiratory chain complex I protein contents at baseline (r = 0.87, P < .0001). Conclusions: Endurance exercise training coordinately up-regulates fat oxidative capacity and lipolytic protein expression in skeletal muscle of obese subjects. This physiological adaptation probably favors fat oxidation and may alleviate the lipotoxic lipid pressure in skeletal muscle. Enhancement of IMTG turnover may be required for the beneficial metabolic effects of exercise in obesity.
43
Vella, Luke, Marissa K. Caldow, Amy E. Larsen, Daniella Tassoni, Paul A. Della Gatta, Petra Gran, Aaron P. Russell, and David Cameron-Smith. "Resistance exercise increases NF-κB activity in human skeletal muscle." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 302, no. 6 (March 15, 2012): R667—R673. http://dx.doi.org/10.1152/ajpregu.00336.2011.
Full textAbstract:
Intense resistance exercise causes a significant inflammatory response. NF-κB has been identified as a prospective key transcription factor mediating the postexercise inflammatory response. The purpose of this study was to determine whether a single bout of intense resistance exercise regulates NF-κB signaling in human skeletal muscle. Muscle biopsy samples were obtained from the vastus lateralis of five recreationally active, but not strength-trained, males (21.9 ± 1.3 yr) prior to, and at 2 and 4 h following, a single bout of intense resistance exercise. A further five subjects (4 males, 1 female) (23 ± 0.89 yr) were recruited as a nonexercise control group to examine the effect of the muscle biopsy protocol on key markers of skeletal muscle inflammation. Protein levels of IκBα and phosphorylated NF-κB (p65), as well as the mRNA expression of inflammatory myokines monocyte chemoattractant protein 1 (MCP-1), IL-6, and IL-8 were measured. Additionally, NF-κB (p65) DNA binding to the promoter regions of MCP-1, IL-6, and IL-8 was investigated. IκBα protein levels decreased, while p-NF-κB (p65) protein levels increased 2 h postexercise and returned to near-baseline levels by 4-h postexercise. Immunohistochemical data verified these findings, illustrating an increase in p-NF-κB (p65) protein levels, and nuclear localization at 2 h postexercise. Furthermore, NF-κB DNA binding to MCP-1, IL-6, and IL-8 promoter regions increased significantly 2 h postexercise as did mRNA levels of these myokines. No significant change was observed in the nonexercise control group. These novel data provide evidence that intense resistance exercise transiently activates NF-κB signaling in human skeletal muscle during the first few hours postexercise. These findings implicate NF-κB in the transcriptional control of myokines known to be central to the postexercise inflammatory response.
44
Taylor, Roy, Thomas B. Price, Douglas L. Rothman, Robert G. Shulman, and Gerald I. Shulman. "Validation of13c nmr measurement of human skeletal muscle glycogen by direct biochemical assay of needle biopsy samples." Magnetic Resonance in Medicine 27, no. 1 (September 1992): 13–20. http://dx.doi.org/10.1002/mrm.1910270103.
Full text
45
Bickel, C. Scott, Jill M. Slade, Fadia Haddad, Gregory R. Adams, and Gary A. Dudley. "Acute molecular responses of skeletal muscle to resistance exercise in able-bodied and spinal cord-injured subjects." Journal of Applied Physiology 94, no. 6 (June 1, 2003): 2255–62. http://dx.doi.org/10.1152/japplphysiol.00014.2003.
Full textAbstract:
Spinal cord injury (SCI) results in muscle atrophy, which contributes to a number of health problems, such as cardiovascular deconditioning, metabolic derangement, and osteoporosis. Electromyostimulation (EMS) holds the promise of ameliorating SCI-related muscle atrophy and, therefore, improving general health. To date, EMS training of long-term SCI subjects has resulted in some muscle hypertrophy but has fallen short of normalizing muscle mass. The aim of this study was to compare the molecular responses of vastus lateralis muscles from able-bodied (AB) and SCI subjects after acute bouts of EMS-induced resistance exercise to determine whether SCI muscles displayed some impairment in response. Analysis included mRNA markers known to be responsive to increased loading in rodent muscles. Muscles of AB and SCI subjects were subjected to EMS-stimulated exercise in two 30-min bouts, separated by a 48-h rest. Needle biopsy samples were obtained 24 h after the second exercise bout. In both the AB and SCI muscles, significant changes were seen in insulin-like growth factor binding proteins 4 and 5, cyclin-dependent kinase inhibitor p21, and myogenin mRNA levels. In AB subjects, the mRNA for mechano-growth factor was also increased. Before exercise, the total RNA concentration of the SCI muscles was less than that of the AB subjects but not different postexercise. The results of this study indicate that acute bouts of resistance exercise stimulate molecular responses in the skeletal muscles of both AB and SCI subjects. The responses seen in the SCI muscles indicate that the systems that regulate these molecular responses are intact, even after extended periods of muscle unloading.
46
Greenhaff, P. L., K. Bodin, K. Soderlund, and E. Hultman. "Effect of oral creatine supplementation on skeletal muscle phosphocreatine resynthesis." American Journal of Physiology-Endocrinology and Metabolism 266, no. 5 (May 1, 1994): E725—E730. http://dx.doi.org/10.1152/ajpendo.1994.266.5.e725.
Full textAbstract:
Biopsy samples were obtained from the vastus lateralis muscle of eight subjects after 0, 20, 60, and 120 s of recovery from intense electrically evoked isometric contraction. Later (10 days), the same procedures were performed using the other leg, but subjects ingested 20 g creatine (Cr)/day for the preceding 5 days. Muscle ATP, phosphocreatine (PCr), free Cr, and lactate concentrations were measured, and total Cr was calculated as the sum of PCr and free Cr concentrations. In five of the eight subjects, Cr ingestion substantially increased muscle total Cr concentration (mean 29 +/- 3 mmol/kg dry matter, 25 +/- 3%; range 19-35 mmol/kg dry matter, 15-32%) and PCr resynthesis during recovery (mean 19 +/- 4 mmol/kg dry matter, 35 +/- 6%; range 11-28 mmol/kg dry matter, 23-53%). In the remaining three subjects, Cr ingestion had little effect on muscle total Cr concentration, producing increases of 8-9 mmol/kg dry matter (5-7%), and did not increase PCr resynthesis. The data suggest that a dietary-induced increase in muscle total Cr concentration can increase PCr resynthesis during the 2nd min of recovery from intense contraction.
47
Mestareehi, Aktham, Xiangmin Zhang, Berhane Seyoum, Zaher Msallaty, Abdullah Mallisho, Kyle Jon Burghardt, Anjaneyulu Kowluru, and Zhengping Yi. "Metformin Increases Protein Phosphatase 2A Activity in Primary Human Skeletal Muscle Cells Derived from Lean Healthy Participants." Journal of Diabetes Research 2021 (July 28, 2021): 1–6. http://dx.doi.org/10.1155/2021/9979234.
Full textAbstract:
Context. Skeletal muscle insulin resistance is one of the primary contributors of type 2 diabetes (T2D). Metformin is the first-line drug for the treatment of T2D. The primary effects of metformin include decreasing glucose production in the liver and decreasing insulin resistance in the skeletal muscle. However, the molecular mechanism of metformin’s action in skeletal muscle is not well understood. Protein phosphatase 2A (PP2A), a major serine/threonine protein phosphatase, plays a pivotal role in cellular processes, such as signal transduction, cell proliferation, and apoptosis, and acts through dephosphorylating key signaling molecules such as AKT and AMPK. However, whether PP2A plays a role in metformin-induced insulin sensitivity improvement in human skeletal muscle cells remains to be elucidated. Objective. To investigate if PP2A plays a role in metformin-induced insulin sensitivity improvement in human skeletal muscle cells. Participants. Eight lean insulin-sensitive nondiabetic participants (4 females and 4 males; age: 21.0 ± 1.0 years; BMI: 22.0 ± 0.7 kg / m 2 ; 2-hour OGTT: 97.0 ± 6.0 mg / dl ; HbA1c: 5.3 ± 0.1 % ; fasting plasma glucose: 87.0 ± 2.0 mg / dl ; M value; 11.0 ± 1.0 mg / kgBW / min ). Design. A hyperinsulinemic-euglycemic clamp was performed to assess insulin sensitivity in human subjects, and skeletal muscle biopsy samples were obtained. Primary human skeletal muscle cells (shown to retain metabolic characteristics of donors) were cultured from these muscle biopsies that included 8 lean insulin-sensitive participants. Cultured cells were expanded, differentiated into myotubes, and treated with 50 μM metformin for 24 hours before harvesting. PP2Ac activity was measured by a phosphatase activity assay kit (Millipore) according to the manufacturer’s protocol. Results. The results indicated that metformin significantly increased the activity of PP2A in the myotubes for all 8 lean insulin-sensitive nondiabetic participants, and the average fold increase is 1.54 ± 0.11 ( P < 0.001 ). Conclusions. These results provided the first evidence that metformin can activate PP2A in human skeletal muscle cells derived from lean healthy insulin-sensitive participants and may help to understand metformin’s action in skeletal muscle in humans.
48
Steinberg, Gregory R., Matthew J. Watt, Sean L. McGee, Stanley Chan, Mark Hargreaves, Mark A. Febbraio, David Stapleton, and Bruce E. Kemp. "Reduced glycogen availability is associated with increased AMPKα2 activity, nuclear AMPKα2 protein abundance, and GLUT4 mRNA expression in contracting human skeletal muscle." Applied Physiology, Nutrition, and Metabolism 31, no. 3 (June 1, 2006): 302–12. http://dx.doi.org/10.1139/h06-003.
Full textAbstract:
Glycogen availability can influence glucose transporter 4 (GLUT4) expression in skeletal muscle through unknown mechanisms. The multisubstrate enzyme AMP-activated protein kinase (AMPK) has also been shown to play an important role in the regulation of GLUT4 expression in skeletal muscle. During contraction, AMPK α2 translocates to the nucleus and the activity of this AMPK isoform is enhanced when skeletal muscle glycogen is low. In this study, we investigated if decreased pre-exercise muscle glycogen levels and increased AMPK α2 activity reduced the association of AMPK with glycogen and increased AMPK α2 translocation to the nucleus and GLUT4 mRNA expression following exercise. Seven males performed 60 min of exercise at ~70% VO2 peak on 2 occasions: either with normal (control) or low (LG) carbohydrate pre-exercise muscle glycogen content. Muscle samples were obtained by needle biopsy before and after exercise. Low muscle glycogen was associated with elevated AMPK α2 activity and acetyl-CoA carboxylase β phosphorylation, increased translocation of AMPK α2 to the nucleus, and increased GLUT4 mRNA. Transfection of primary human myotubes with a constitutively active AMPK adenovirus also stimulated GLUT4 mRNA, providing direct evidence of a role of AMPK in regulating GLUT4 expression. We suggest that increased activation of AMPK α2 under conditions of low muscle glycogen enhances AMPK α2 nuclear translocation and increases GLUT4 mRNA expression in response to exercise in human skeletal muscle.Key words: exercise, subcellular localization, glycogen binding domain, AMP-activated protein kinase.
49
Oliveira, Acary Souza Bulle, Massimo Corbo, Greg Duigou, Alberto Alain Gabbai, and Arthur P. Hays. "Expression of a cell death marker (clusterin) in muscle target fibers." Arquivos de Neuro-Psiquiatria 51, no. 3 (September 1993): 371–76. http://dx.doi.org/10.1590/s0004-282x1993000300014.
Full textAbstract:
We report, for the first time, the expression of immunoractivity to clusterin in skeletal muscle. Clusterin, a protein probably related to the process of programmed cell death (apoptosis), was specifically very highly expressed in target fibers. All target fibers found in 50 muscle biopsy samples from a variety of neuromuscular disorders expressed a high concentration of clusterin in the middle of the targets. Clusterin was not expressed in any targetoid fibers or cores. Acute denervation, where targets are mostly seen, may be the beginning of apoptosis. Hence our findings support the concept that targets are harbingers of acute denervation.
50
Nair, K. S., D. Halliday, and R. C. Griggs. "Leucine incorporation into mixed skeletal muscle protein in humans." American Journal of Physiology-Endocrinology and Metabolism 254, no. 2 (February 1, 1988): E208—E213. http://dx.doi.org/10.1152/ajpendo.1988.254.2.e208.
Full textAbstract:
Fractional mixed skeletal muscle protein synthesis (FMPS) was estimated in 10 postabsorptive healthy men by determining the increment in the abundance of [13C]-leucine in quadriceps muscle protein during an intravenous infusion of L-[1-13C]leucine. FMPS in our subjects was 0.046 +/- 0.003%/h. Whole-body muscle protein synthesis (MPS) was calculated based on the estimation of muscle mass from creatinine excretion and compared with whole-body protein synthesis (WBPS) calculated from the nonoxidative portion of leucine flux. A significant correlation (r2 = 0.73, P less than 0.05) was found between MPS (44.7 +/- 3.4 mg.kg-1.h-1) and WBPS (167.8 +/- 8.5 mg.kg-1.h-1). The contribution of MPS to WBPS was 27 +/- 1%, which is comparable to the reports in other species. Morphometric analyses of adjacent muscle samples in eight subjects demonstrated that the biopsy specimens consisted of 86.5 +/- 2% muscular as opposed to other tissues. Because fiber type composition varies between biopsies, we examined the relationship between proportions of each fiber type and FMPS. Variation in the composition of biopsies and in fiber-type proportion did not affect the estimation of muscle protein synthesis rate. We conclude that stable isotope techniques using serial needle biopsies permit the direct measurement of FMPS in humans and that this estimation is correlated with an indirect estimation of WBPS.