The ERG1 Potassium Channel is More Abundant in Skeletal Muscle from Cachectic than Healthy Humans

Abstract Background: The ERG1a potassium channel has been detected in the atrophying skeletal muscle of mice experiencing either muscle disuse or cancer cachexia and further evidenced to contribute to muscle deterioration by enhancing ubiquitin proteolysis; however, to our knowledge, ERG1 has not been reported in human skeletal muscle. Methods and Results: Here, using immunohistochemistry, we detect ERG1 immunofluorescence in human Rectus abdominis skeletal muscle sarcolemma. Further, using single point brightness data, we report detection of ERG1 immunofluorescence at low levels in the Rectus abdominis muscle sarcolemma of young adult humans and show that it trends toward greater levels (10.6%) in healthy aged adults. Interestingly, we detect ERG1 immunofluorescence at a statistically greater level (53.6%; p<0.05) in the skeletal muscle of older people having cancer cachexia than in age-matched adults. Importantly, using immunoblot, we reveal that ERG1 protein is 38% (p<0.09) more abundant in the skeletal muscle of cachectic older adults than in healthy age-matched controls. Additionally, we report that the ERG1 fluorescent pattern is consistent with I-band localization. Conclusions: The data suggest that ERG1 may be related to muscle loss in humans and is located in t-tubules where it could influence calcium handling.

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The ERG1A K+ Channel Is More Abundant in Rectus abdominis Muscle from Cancer Patients Than that from Healthy Humans

Diagnostics ◽

10.3390/diagnostics11101879 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1879

Author(s):

Sandra Zampieri ◽

Marco Sandri ◽

Joseph L. Cheatwood ◽

Rajesh P. Balaraman ◽

Luke B. Anderson ◽

...

Keyword(s):

Skeletal Muscle ◽

Cancer Patients ◽

Malignant Tumors ◽

Single Point ◽

Rectus Abdominis ◽

K Channel ◽

Rectus Abdominis Muscle ◽

Healthy Humans ◽

Vitro Model

Background: The potassium channel encoded by the ether-a-gogo-related gene 1A (erg1a) has been detected in the atrophying skeletal muscle of mice experiencing either muscle disuse or cancer cachexia and further evidenced to contribute to muscle deterioration by enhancing ubiquitin proteolysis; however, to our knowledge, ERG1A has not been reported in human skeletal muscle. Methods and Results: Here, using immunohistochemistry, we detect ERG1A immunofluorescence in human Rectus abdominis skeletal muscle sarcolemma. Further, using single point brightness data, we report the detection of ERG1A immunofluorescence at low levels in the Rectus abdominis muscle sarcolemma of young adult humans and show that it trends toward greater levels (10.6%) in healthy aged adults. Interestingly, we detect ERG1A immunofluorescence at a statistically greater level (53.6%; p < 0.05) in the skeletal muscle of older cancer patients than in age-matched healthy adults. Importantly, using immunoblot, we reveal that lower mass ERG1A protein is 61.5% (p < 0.05) more abundant in the skeletal muscle of cachectic older adults than in healthy age-matched controls. Additionally, we report that the ERG1A protein is detected in a cultured human rhabdomyosarcoma line that may be a good in vitro model for the study of ERG1A in muscle. Conclusions: The data demonstrate that ERG1A is detected more abundantly in the atrophied skeletal muscle of cancer patients, suggesting it may be related to muscle loss in humans as it has been shown to be in mice experiencing muscle atrophy as a result of malignant tumors.

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A Time-Course Comparison of Skeletal Muscle Metabolomic Alterations in Walker-256 Tumour-Bearing Rats at Different Stages of Life

Metabolites ◽

10.3390/metabo11060404 ◽

2021 ◽

Vol 11 (6) ◽

pp. 404

Author(s):

Gabriela de Matuoka e Chiocchetti ◽

Leisa Lopes-Aguiar ◽

Natália Angelo da Silva Miyaguti ◽

Lais Rosa Viana ◽

Carla de Moraes Salgado ◽

...

Keyword(s):

Skeletal Muscle ◽

Time Course ◽

Cancer Cachexia ◽

Tumour Bearing ◽

Walker 256 Tumour ◽

Walker 256 ◽

Muscle Changes ◽

The Right ◽

Biomarker Research ◽

Host Metabolism

Cancer cachexia is a severe wasting condition that needs further study to find ways to minimise the effects of damage and poor prognosis. Skeletal muscle is the most impacted tissue in cancer cachexia; thus, elucidation of its metabolic alterations could provide a direct clue for biomarker research and be applied to detect this syndrome earlier. In addition, concerning the significant changes in the host metabolism across life, this study aimed to compare the metabolic muscle changes in cachectic tumour-bearing hosts at different ages. We performed 1H-NMR metabolomics in the gastrocnemius muscle in weanling and young adult Walker-256 tumour-bearing rats at different stages of tumour evolution (initial, intermediate, and advanced). Among the 49 metabolites identified, 24 were significantly affected throughout tumour evolution and 21 were significantly affected regarding animal age. The altered metabolites were mainly related to increased amino acid levels and changed energetic metabolism in the skeletal muscle, suggesting an expressive catabolic process and diverted energy production, especially in advanced tumour stages in both groups. Moreover, these changes were more severe in weanling hosts throughout tumour evolution, suggesting the distinct impact of cancer cachexia regarding the host’s age, highlighting the need to adopting the right animal age when studying cancer cachexia.

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Chronic Ouabain Prevents Na,K-ATPase Dysfunction and Targets AMPK and IL-6 in Disused Rat Soleus Muscle

International Journal of Molecular Sciences ◽

10.3390/ijms22083920 ◽

2021 ◽

Vol 22 (8) ◽

pp. 3920

Author(s):

Violetta V. Kravtsova ◽

Inna I. Paramonova ◽

Natalia A. Vilchinskaya ◽

Maria V. Tishkova ◽

Vladimir V. Matchkov ◽

...

Keyword(s):

Skeletal Muscle ◽

Single Injection ◽

Chronic Administration ◽

Motor Dysfunction ◽

Hindlimb Suspension ◽

Muscle Disuse ◽

Rat Soleus Muscle ◽

Amp Activated Protein Kinase ◽

Specific Ligand

Sustained sarcolemma depolarization due to loss of the Na,K-ATPase function is characteristic for skeletal muscle motor dysfunction. Ouabain, a specific ligand of the Na,K-ATPase, has a circulating endogenous analogue. We hypothesized that the Na,K-ATPase targeted by the elevated level of circulating ouabain modulates skeletal muscle electrogenesis and prevents its disuse-induced disturbances. Isolated soleus muscles from rats intraperitoneally injected with ouabain alone or subsequently exposed to muscle disuse by 6-h hindlimb suspension (HS) were studied. Conventional electrophysiology, Western blotting, and confocal microscopy with cytochemistry were used. Acutely applied 10 nM ouabain hyperpolarized the membrane. However, a single injection of ouabain (1 µg/kg) prior HS was unable to prevent the HS-induced membrane depolarization. Chronic administration of ouabain for four days did not change the α1 and α2 Na,K-ATPase protein content, however it partially prevented the HS-induced loss of the Na,K-ATPase electrogenic activity and sarcolemma depolarization. These changes were associated with increased phosphorylation levels of AMP-activated protein kinase (AMPK), its substrate acetyl-CoA carboxylase and p70 protein, accompanied with increased mRNA expression of interleikin-6 (IL-6) and IL-6 receptor. Considering the role of AMPK in regulation of the Na,K-ATPase, we suggest an IL-6/AMPK contribution to prevent the effects of chronic ouabain under skeletal muscle disuse.

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Anorexia decreases skeletal muscle protein synthesis in cancer cachexia

Clinical Nutrition ◽

10.1016/0261-5614(82)90252-7 ◽

1982 ◽

Vol 1 ◽

pp. 131

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Cancer Cachexia ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Skeletal Muscle Protein ◽

Skeletal Muscle Protein Synthesis

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Skeletal muscle PGC-1β signaling is sufficient to drive an endurance exercise phenotype and to counteract components of detraining in mice

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00380.2016 ◽

2017 ◽

Vol 312 (5) ◽

pp. E394-E406 ◽

Cited By ~ 10

Author(s):

Samuel Lee ◽

Teresa C. Leone ◽

Lisa Rogosa ◽

John Rumsey ◽

Julio Ayala ◽

...

Keyword(s):

Skeletal Muscle ◽

Exercise Training ◽

Early Stage ◽

Peroxisome Proliferator ◽

Disuse Atrophy ◽

Proof Of Concept ◽

Peroxisome Proliferator Activated Receptor ◽

Muscle Disuse ◽

Training Response

Peroxisome proliferator-activated receptor-γ coactivator (PGC)-1α and -1β serve as master transcriptional regulators of muscle mitochondrial functional capacity and are capable of enhancing muscle endurance when overexpressed in mice. We sought to determine whether muscle-specific transgenic overexpression of PGC-1β affects the detraining response following endurance training. First, we established and validated a mouse exercise-training-detraining protocol. Second, using multiple physiological and gene expression end points, we found that PGC-1β overexpression in skeletal muscle of sedentary mice fully recapitulated the training response. Lastly, PGC-1β overexpression during the detraining period resulted in partial prevention of the detraining response. Specifically, an increase in the plateau at which O2 uptake (V̇o2) did not change from baseline with increasing treadmill speed [peak V̇o2 (ΔV̇o2max)] was maintained in trained mice with PGC-1β overexpression in muscle 6 wk after cessation of training. However, other detraining responses, including changes in running performance and in situ half relaxation time (a measure of contractility), were not affected by PGC-1β overexpression. We conclude that while activation of muscle PGC-1β is sufficient to drive the complete endurance phenotype in sedentary mice, it only partially prevents the detraining response following exercise training, suggesting that the process of endurance detraining involves mechanisms beyond the reversal of muscle autonomous mechanisms involved in endurance fitness. In addition, the protocol described here should be useful for assessing early-stage proof-of-concept interventions in preclinical models of muscle disuse atrophy.

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Reorganized stores and impaired calcium handling in skeletal muscle of mice lacking calsequestrin-1

The Journal of Physiology ◽

10.1113/jphysiol.2007.138024 ◽

2007 ◽

Vol 583 (2) ◽

pp. 767-784 ◽

Cited By ~ 103

Author(s):

Cecilia Paolini ◽

Marco Quarta ◽

Alessandra Nori ◽

Simona Boncompagni ◽

Marta Canato ◽

...

Keyword(s):

Skeletal Muscle ◽

Calcium Handling

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Physical exercise increases autophagic signaling through ULK1 in human skeletal muscle

Journal of Applied Physiology ◽

10.1152/japplphysiol.01116.2014 ◽

2015 ◽

Vol 118 (8) ◽

pp. 971-979 ◽

Cited By ~ 58

Author(s):

Andreas Buch Møller ◽

Mikkel Holm Vendelbo ◽

Britt Christensen ◽

Berthil Forrest Clasen ◽

Ann Mosegaard Bak ◽

...

Keyword(s):

Skeletal Muscle ◽

Physical Exercise ◽

Light Chain ◽

Human Skeletal Muscle ◽

Transgenic Animal ◽

Dependent Manner ◽

Healthy Humans ◽

Transgenic Animal Models ◽

Exercise Induced

Data from transgenic animal models suggest that exercise-induced autophagy is critical for adaptation to physical training, and that Unc-51 like kinase-1 (ULK1) serves as an important regulator of autophagy. Phosphorylation of ULK1 at Ser555 stimulates autophagy, whereas phosphorylation at Ser757 is inhibitory. To determine whether exercise regulates ULK1 phosphorylation in humans in vivo in a nutrient-dependent manner, we examined skeletal muscle biopsies from healthy humans after 1-h cycling exercise at 50% maximal O2 uptake on two occasions: 1) during a 36-h fast, and 2) during continuous glucose infusion at 0.2 kg/h. Physical exercise increased ULK1 phosphorylation at Ser555 and decreased lipidation of light chain 3B. ULK1 phosphorylation at Ser555 correlated positively with AMP-activated protein kinase-α Thr172 phosphorylation and negatively with light chain 3B lipidation. ULK1 phosphorylation at Ser757 was not affected by exercise. Fasting increased ULK1 and p62 protein expression, but did not affect exercise-induced ULK1 phosphorylation. These data demonstrate that autophagy signaling is activated in human skeletal muscle after 60 min of exercise, independently of nutritional status, and suggest that initiation of autophagy constitutes an important physiological response to exercise in humans.

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AML1 is expressed in skeletal muscle and is regulated by innervation

Molecular and Cellular Biology ◽

10.1128/mcb.14.12.8051-8057.1994 ◽

1994 ◽

Vol 14 (12) ◽

pp. 8051-8057

Author(s):

X Zhu ◽

J E Yeadon ◽

S J Burden

Keyword(s):

Skeletal Muscle ◽

Acute Myeloid Leukemia ◽

Electrical Activity ◽

Myeloid Leukemia ◽

Structure And Function ◽

Denervated Muscle ◽

Aml1 Gene ◽

Low Levels ◽

And Function ◽

Acute Myeloid

Although most skeletal muscle genes are expressed at similar levels in electrically active, innervated muscle and in electrically inactive, denervated muscle, a small number of genes, including those encoding the acetylcholine receptor, N-CAM, and myogenin, are expressed at significantly higher levels in denervated than in innervated muscle. The mechanisms that mediate electrical activity-dependent gene regulation are not understood, but these mechanisms are likely to be responsible, at least in part, for the changes in muscle structure and function that accompany a decrease in myofiber electrical activity. To understand how muscle activity regulates muscle structure and function, we used a subtractive-hybridization and cloning strategy to identify and isolate genes that are expressed preferentially in innervated or denervated muscle. One of the genes which we found to be regulated by electrical activity is the recently discovered acute myeloid leukemia 1 (AML1) gene. Disruption and translocation of the human AML1 gene are responsible for a form of acute myeloid leukemia. AML1 is a DNA-binding protein, but its normal function is not known and its expression and regulation in skeletal muscle were not previously appreciated. Because of its potential role as a transcriptional mediator of electrical activity, we characterized expression of the AML1 gene in innervated, denervated, and developing skeletal muscle. We show that AML1 is expressed at low levels in innervated skeletal muscle and at 50- to 100-fold-higher levels in denervated muscle. Four AML1 transcripts are expressed in denervated muscle, and the abundance of each transcript increases after denervation. We transfected C2 muscle cells with an expression vector encoding AML1, tagged with an epitope from hemagglutinin, and we show that AML1 is a nuclear protein in muscle. AML1 dimerizes with core-binding factor beta (CBF beta), and we show that CGF beta is expressed at high levels in both innervated and denervated skeletal muscle. PEBP2 alpha, which is structurally related to AML1 and which also dimerizes with CBF beta, is expressed at low levels in skeletal muscle and is up-regulated only weakly by denervation. These results are consistent with the idea that AML1 may have a role in regulating gene expression in skeletal muscle.

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Differential energetic response of brain vs. skeletal muscle upon glycemic variations in healthy humans

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00093.2007 ◽

2008 ◽

Vol 294 (1) ◽

pp. R12-R16 ◽

Cited By ~ 26

Author(s):

Kerstin M. Oltmanns ◽

Uwe H. Melchert ◽

Harald G. Scholand-Engler ◽

Maria C. Howitz ◽

Bernd Schultes ◽

...

Keyword(s):

Skeletal Muscle ◽

Underlying Mechanism ◽

High Energy ◽

Resonance Spectroscopy ◽

Energy Status ◽

High Energy Phosphate ◽

Available Energy ◽

Healthy Humans ◽

High Energy Phosphate Metabolism ◽

The Brain

The brain regulates all metabolic processes within the organism, and therefore, its energy supply is preserved even during fasting. However, the underlying mechanism is unknown. Here, it is shown, using 31P-magnetic resonance spectroscopy that during short periods of hypoglycemia and hyperglycemia, the brain can rapidly increase its high-energy phosphate content, whereas there is no change in skeletal muscle. We investigated the key metabolites of high-energy phosphate metabolism as rapidly available energy stores by 31P MRS in brain and skeletal muscle of 17 healthy men. Measurements were performed at baseline and during dextrose or insulin-induced hyperglycemia and hypoglycemia. During hyperglycemia, phosphocreatine (PCr) concentrations increased significantly in the brain ( P = 0.013), while there was a similar trend in the hypopglycemic condition ( P = 0.055). Skeletal muscle content remained constant in both conditions ( P > 0.1). ANOVA analyses comparing changes from baseline to the respective glycemic plateau in brain (up to +15%) vs. muscle (up to −4%) revealed clear divergent effects in both conditions ( P < 0.05). These effects were reflected by PCr/Pi ratio ( P < 0.05). Total ATP concentrations revealed the observed divergency only during hyperglycemia ( P = 0.018). These data suggest that the brain, in contrast to peripheral organs, can activate some specific mechanisms to modulate its energy status during variations in glucose supply. A disturbance of these mechanisms may have far-reaching implications for metabolic dysregulation associated with obesity or diabetes mellitus.

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