scholarly journals Transient neonatal exposure to hyperoxia, an experimental model of preterm birth, leads to skeletal muscle atrophy and fiber type switching

2021 ◽  
Author(s):  
Alyson Deprez ◽  
Zakaria Orfi ◽  
Alexandra Radu ◽  
Ying He ◽  
Daniela Ravizzoni Dartora ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Preterm Birth ◽  
Exercise Capacity ◽  
Skeletal Muscles ◽  
Fiber Type ◽  
Female Rats ◽  
Male Rats ◽  
Antioxidant Defenses ◽  
Increased Risk ◽  
And Function

Individuals born preterm show reduced exercise capacity and increased risk for pulmonary and cardiovascular diseases, but the impact of preterm birth on skeletal muscle, an inherently critical part of cardiorespiratory fitness, remains unknown. We evaluated the impacts of preterm birth-related conditions on the development, growth, and function of skeletal muscle using a recognized preclinical rodent model in which newborn rats are exposed to 80% oxygen from day 3 to 10 of life. We analyzed different hindlimb muscles of male and female rats at 10 days (neonatal), 4 weeks (juvenile) and 16 weeks (young adults). Neonatal high oxygen exposure increased the generation of reactive oxygen species and the signs of inflammation in skeletal muscles, which was associated with muscle fiber atrophy, fiber type shifting (reduced proportion of type I slow fibers and increased proportion of type IIb fast-fatigable fibers), and impairment in muscle function. These effects were maintained until adulthood. Fast-twitch muscles were more vulnerable to the effects of hyperoxia than slow-twitch muscles. Male rats, which expressed lower antioxidant defenses, were more susceptible than females to oxygen-induced myopathy. Overall, preterm birth-related conditions have long-lasting effects on the composition, morphology, and function of skeletal muscles; and these effects are sex-specific. Oxygen-induced changes in skeletal muscles could contribute to the reduced exercise capacity and to increased risk of diseases of preterm born individuals.

scholarly journals Skeletal muscle fiber-type switching, myopathy, and exercise intolerance in Sigmar1 null mice

2021 ◽  
Author(s):  
Richa Aishwarya ◽  
Chowdhury Abdullah ◽  
Naznin Remex ◽  
Shafiul Alam ◽  
Mahboob Morshed ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Skeletal Muscles ◽  
Physiological Function ◽  
Fiber Type ◽  
Structure And Function ◽  
Exercise Intolerance ◽  
Type I ◽  
Motor Neuropathy ◽  
Muscle Structure ◽  
And Function

Abstract Sigmar1 is a widely expressed, multitasking molecular chaperone protein playing functional roles in several cellular processes. Mutations in the Sigmar1 gene have been reported to associate with several motor neuropathies, including amyotrophic lateral sclerosis, distal hereditary motor neuropathy, silver-like syndrome, and frontotemporal lobar degeneration. All these human mutations associated with motor neuropathies show strong manifestation in skeletal muscle with phenotypes like muscle wasting and atrophy. However, the physiological function of Sigmar1 in skeletal muscle remains unexplored. Here, we determined the physiological role of Sigmar1 in skeletal muscle structure and function in five different skeletal muscles: gastrocnemius (Gastro), quadriceps (Quad), soleus (Sol), extensor digitorum longus (EDL), and tibialis anterior (TA). Quantification of myofiber cross-sectional area (CSA) showed altered muscle mass and a slow-to-fast fiber-type switch in the skeletal muscle fibers of the Sigmar1−/− mice. Interestingly, ultrastructural analysis by transmission electron microscopy showed the presence of tubular aggregates in the type I myofibers (Gastro, Quad, and TA) of Sigmar1−/− mice. Immunostaining also showed derangements in dystrophin localization in skeletal muscles from Sigmar1−/− mice. Additionally, skeletal muscle myopathy in Sigmar1−/− mice was associated with an increased number of central nuclei, increased collagen deposition, and fibrosis. Functional studies also showed reduced endurance and exercise capacity in the Sigmar1−/− mice. Overall, our studies demonstrated, for the first time, a potential physiological function of Sigmar1 in the skeletal muscle in maintaining healthy muscle structure and function.

scholarly journals Kidney Injury Caused by Preeclamptic Pregnancy Recovers Postpartum in a Transgenic Rat Model

2021 ◽  
Vol 22 (7) ◽  
pp. 3762
Author(s):  
Sarah M. Kedziora ◽  
Kristin Kräker ◽  
Lajos Markó ◽  
Julia Binder ◽  
Meryam Sugulle ◽  
...  
Keyword(s):  
Rat Model ◽  
Renal Damage ◽  
Kidney Injury ◽  
Tissue Growth ◽  
Female Rats ◽  
Male Rats ◽  
Renal Diseases ◽  
Transgenic Rat ◽  
Increased Risk ◽  
Before And After

Preeclampsia (PE) is characterized by the onset of hypertension (≥140/90 mmHg) and presence of proteinuria (>300 mg/L/24 h urine) or other maternal organ dysfunctions. During human PE, renal injuries have been observed. Some studies suggest that women with PE diagnosis have an increased risk to develop renal diseases later in life. However, in human studies PE as a single cause of this development cannot be investigated. Here, we aimed to investigate the effect of PE on postpartum renal damage in an established transgenic PE rat model. Female rats harboring the human-angiotensinogen gene develop a preeclamptic phenotype after mating with male rats harboring the human-renin gene, but are normotensive before and after pregnancy. During pregnancy PE rats developed mild tubular and glomerular changes assessed by histologic analysis, increased gene expression of renal damage markers such as kidney injury marker 1 and connective-tissue growth factor, and albuminuria compared to female wild-type rats (WT). However, four weeks postpartum, most PE-related renal pathologies were absent, including albuminuria and elevated biomarker expression. Only mild enlargement of the glomerular tuft could be detected. Overall, the glomerular and tubular function were affected during pregnancy in the transgenic PE rat. However, almost all these pathologies observed during PE recovered postpartum.

Glutamine synthetase induction by glucocorticoids is preserved in skeletal muscle of aged rats

1996 ◽  
Vol 271 (6) ◽  
pp. E1061-E1066 ◽  
Author(s):  
D. Meynial-Denis ◽  
M. Mignon ◽  
A. Miri ◽  
J. Imbert ◽  
E. Aurousseau ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glutamine Synthetase ◽  
Skeletal Muscles ◽  
Female Rats ◽  
Mrna Levels ◽  
Aged Rats ◽  
Adult Rats ◽  
Adult Age ◽  
Slow Twitch ◽  
Fast Twitch

Glutamine synthetase (GS) is a glucocorticoid-inducible enzyme that has a key role for glutamine synthesis in muscle. We hypothesized that the glucocorticoid induction of GS could be altered in aged rats, because alterations in the responsiveness of some genes to glucocorticoids were reported in aging. We compared the glucocorticoid-induced GS in fast-twitch and slow-twitch skeletal muscles (tibialis anterior and soleus, respectively) and heart from adult (age 6-8 mo) and aged (age 22 mo) female rats. All animals received dexamethasone (Dex) in their drinking water (0.77 +/- 0.10 and 0.80 +/- 0.08 mg/day per adult and aged rat, respectively) for 5 days. Dex caused an increase in both GS activity and GS mRNA in fast-twitch and slow-twitch skeletal muscles from adult and aged rats. In contrast, Dex increased GS activity in heart of adult rats, without any concomitant change in GS mRNA levels. Furthermore, Dex did not affect GS activity in aged heart. Thus the responsiveness of GS to an excess of glucocorticoids is preserved in skeletal muscle but not in heart from aged animals.

Effect of microgravity on the expression of mitochondrial enzymes in rat cardiac and skeletal muscles

1998 ◽  
Vol 84 (2) ◽  
pp. 593-598 ◽  
Author(s):  
Michael K. Connor ◽  
David A. Hood
Keyword(s):  
Skeletal Muscle ◽  
Enzyme Activity ◽  
Skeletal Muscles ◽  
Male Rats ◽  
Mitochondrial Enzymes ◽  
Mrna Levels ◽  
Triceps Brachii ◽  
Protein Levels ◽  
Functional Consequences ◽  
Microgravity Conditions

Connor, Michael K., and David A. Hood. Effect of microgravity on the expression of mitochondrial enzymes in rat cardiac and skeletal muscles. J. Appl. Physiol. 84(2): 593–598, 1998.—The purpose of this study was to examine the expression of nuclear and mitochondrial genes in cardiac and skeletal muscle (triceps brachii) in response to short-duration microgravity exposure. Six adult male rats were exposed to microgravity for 6 days and were compared with six ground-based control animals. We observed a significant 32% increase in heart malate dehydrogenase (MDH) enzyme activity, which was accompanied by a 62% elevation in heart MDH mRNA levels after microgravity exposure. Despite modest elevations in the mRNAs encoding subunits III, IV, and VIc as well as a 2.2-fold higher subunit IV protein content after exposure to microgravity, heart cytochrome c oxidase (CytOx) enzyme activity remained unchanged. In skeletal muscle, MDH expression was unaffected by microgravity, but CytOx activity was significantly reduced 41% by microgravity, whereas subunit III, IV, and VIc mRNA levels and subunit IV protein levels were unaltered. Thus tissue-specific (i.e., heart vs. skeletal muscle) differences exist in the regulation of nuclear-encoded mitochondrial proteins in response to microgravity. In addition, the expression of nuclear-encoded proteins such as CytOx subunit IV and expression of MDH are differentially regulated within a tissue. Our data also illustrate that the heart undergoes previously unidentified mitochondrial adaptations in response to short-term microgravity conditions more dramatic than those evident in skeletal muscle. Further studies evaluating the functional consequences of these adaptations in the heart, as well as those designed to measure protein turnover, are warranted in response to microgravity.

scholarly journals Effects of Ovariectomy on Skeletal Muscle Structure and Function in Young Female Rats: Protective Effects of the Flavanol (−)‐Epicatechin

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Viridiana Navarrrete ◽  
Marcos Ayala ◽  
Antonio Rodriguez ◽  
Francisco Villarreal ◽  
Israel Ramirez-Sanchez
Keyword(s):  
Skeletal Muscle ◽  
Young Female ◽  
Structure And Function ◽  
Female Rats ◽  
Protective Effects ◽  
Muscle Structure ◽  
And Function

Effect of diltiazem on skeletal muscle 3-O-methylglucose transport in bacteremic rats

1989 ◽  
Vol 256 (3) ◽  
pp. R716-R721
Author(s):  
M. V. Westfall ◽  
M. M. Sayeed
Keyword(s):  
Escherichia Coli ◽  
Skeletal Muscle ◽  
Low Temperature ◽  
Skeletal Muscles ◽  
Cytochalasin B ◽  
Sugar Transport ◽  
Male Rats ◽  
Saline Control ◽  
Permeability Changes

This study examined whether alterations in cellular Ca2+ regulation contribute to previously observed changes in skeletal muscle sugar transport during bacteremia. Fasted male rats received saline (control) or bacteria (4 X 10(10) Escherichia coli/kg) intraperitoneally. Twelve hours later, basal and insulin-mediated 3-O-methylglucose (3MG) transport was measured in isolated soleus muscles. Measurements of 3MG transport in the presence of cytochalasin b or at a low temperature (0.5 degree C) indicated that altered sugar transport in bacteremic rat muscles was not due to nonspecific membrane permeability changes. To determine the role of Ca2+ in the pathogenesis of altered sugar transport during bacteremia, rats were treated with the Ca2+ antagonist diltiazem (DZ, 0.6-2.4 mg/kg) at various times (0, 0 + 7.5, 10 h) after saline or bacterial injection. In bacteremic rats given 2.4 mg/kg DZ at 10 h, basal and insulin-mediated transport were similar to control values. This dose of DZ had little effect on control muscles. The addition of 20 microM DZ to the incubation media did not affect basal or insulin-mediated 3MG transport in bacteremic rat muscles. Addition of the Ca2+ agonist BAY K 8644 to the incubation media had no effect on sugar transport in bacteremic rat muscles but caused alterations in control rat muscles that were comparable to those observed in bacteremia. These results suggest that alterations in Ca2+ regulation could contribute to the previously observed changes in sugar transport in skeletal muscles from bacteremic rats.

scholarly journals Two Weeks of Smoking Cessation Reverse Cigarette Smoke-Induced Skeletal Muscle Atrophy and Mitochondrial Dysfunction in Mice

2020 ◽  
Author(s):  
Tom Tanjeko Ajime ◽  
Jef Serré ◽  
Rob C I Wüst ◽  
Guy Anselme Mpaka Messa ◽  
Chiel Poffé ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Smoking Cessation ◽  
Mitochondrial Dysfunction ◽  
Muscle Mass ◽  
Muscle Atrophy ◽  
Skeletal Muscles ◽  
Skeletal Muscle Atrophy ◽  
Limb Muscle ◽  
Male Mice ◽  
And Function

Abstract Introduction Apart from its adverse effects on the respiratory system, cigarette smoking also induces skeletal muscle atrophy and dysfunction. Whether short-term smoking cessation can restore muscle mass and function is unknown. We, therefore, studied the impact of 1- and 2-week smoking cessation on skeletal muscles in a mouse model. Methods Male mice were divided into four groups: Air-exposed (14 weeks); cigarette smoke (CS)-exposed (14 weeks); CS-exposed (13 weeks) followed by 1-week cessation; CS-exposed (12 weeks) followed by 2 weeks cessation to examine exercise capacity, physical activity levels, body composition, muscle function, capillarization, mitochondrial function and protein expression in the soleus, plantaris, and diaphragm muscles. Results CS-induced loss of body and muscle mass was significantly improved within 1 week of cessation due to increased lean and fat mass. Mitochondrial respiration and protein levels of the respiratory complexes in the soleus were lower in CS-exposed mice, but similar to control values after 2 weeks of cessation. Exposing isolated soleus muscles to CS extracts reduced mitochondrial respiration that was reversed after removing the extract. While physical activity was reduced in all groups, exercise capacity, limb muscle force, fatigue resistance, fiber size and capillarization, and diaphragm cytoplasmic HIF-1α were unaltered by CS-exposure. However, CS-induced diaphragm atrophy and increased capillary density were not seen after 2 weeks of smoking cessation. Conclusion In male mice, 2 weeks of smoking cessation reversed smoking-induced mitochondrial dysfunction, limb muscle mass loss, and diaphragm muscle atrophy, highlighting immediate benefits of cessation on skeletal muscles. Implications Our study demonstrates that CS-induced skeletal muscle mitochondrial dysfunction and atrophy are significantly improved by 2 weeks of cessation in male mice. We show for the first time that smoking cessation as short as 1 to 2 weeks is associated with immediate beneficial effects on skeletal muscle structure and function with the diaphragm being particularly sensitive to CS-exposure and cessation. This could help motivate smokers to quit smoking as early as possible. The knowledge that smoking cessation has potential positive extrapulmonary effects is particularly relevant for patients referred to rehabilitation programs and those admitted to hospitals suffering from acute or chronic muscle deterioration yet struggling with smoking cessation.

scholarly journals Skeletal muscle fiber type-selective effects of acute exercise on insulin-stimulated glucose uptake in insulin-resistant, high-fat-fed rats

2019 ◽  
Vol 316 (5) ◽  
pp. E695-E706 ◽  
Author(s):  
Mark W. Pataky ◽  
Carmen S. Yu ◽  
Yilin Nie ◽  
Edward B. Arias ◽  
Manak Singh ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Acute Exercise ◽  
Fiber Type ◽  
Single Fiber ◽  
Male Rats ◽  
Type I ◽  
Fiber Types ◽  
High Fat ◽  
Insulin Resistant

Insulin-stimulated glucose uptake (GU) by skeletal muscle is enhanced several hours after acute exercise in rats with normal or reduced insulin sensitivity. Skeletal muscle is composed of multiple fiber types, but exercise’s effect on fiber type-specific insulin-stimulated GU in insulin-resistant muscle was previously unknown. Male rats were fed a high-fat diet (HFD; 2 wk) and were either sedentary (SED) or exercised (2-h exercise). Other, low-fat diet-fed (LFD) rats remained SED. Rats were studied immediately postexercise (IPEX) or 3 h postexercise (3hPEX). Epitrochlearis muscles from IPEX rats were incubated in 2-deoxy-[3H]glucose (2-[3H]DG) without insulin. Epitrochlearis muscles from 3hPEX rats were incubated with 2-[3H]DG ± 100 µU/ml insulin. After single fiber isolation, GU and fiber type were determined. Glycogen and lipid droplets (LDs) were assessed histochemically. GLUT4 abundance was determined by immunoblotting. In HFD-SED vs. LFD-SED rats, insulin-stimulated GU was decreased in type IIB, IIX, IIAX, and IIBX fibers. Insulin-independent GU IPEX was increased and glycogen content was decreased in all fiber types (types I, IIA, IIB, IIX, IIAX, and IIBX). Exercise by HFD-fed rats enhanced insulin-stimulated GU in all fiber types except type I. Single fiber analyses enabled discovery of striking fiber type-specific differences in HFD and exercise effects on insulin-stimulated GU. The fiber type-specific differences in insulin-stimulated GU postexercise in insulin-resistant muscle were not attributable to a lack of fiber recruitment, as indirectly evidenced by insulin-independent GU and glycogen IPEX, differences in multiple LD indexes, or altered GLUT4 abundance, implicating fiber type-selective differences in the cellular processes responsible for postexercise enhancement of insulin-mediated GLUT4 translocation.

scholarly journals Overexpression of TRB3 in muscle alters muscle fiber type and improves exercise capacity in mice

2014 ◽  
Vol 306 (12) ◽  
pp. R925-R933 ◽  
Author(s):  
Ding An ◽  
Sarah J. Lessard ◽  
Taro Toyoda ◽  
Min-Young Lee ◽  
Ho-Jin Koh ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Exercise Capacity ◽  
Muscle Fiber ◽  
Wheel Running ◽  
Fiber Type ◽  
Muscle Fiber Type ◽  
Acid Oxidation ◽  
Peroxisome Proliferator ◽  
Type I ◽  
Pronounced Increase

Increasing evidence suggests that TRB3, a mammalian homolog of Drosophila tribbles, plays an important role in cell growth, differentiation, and metabolism. In the liver, TRB3 binds and inhibits Akt activity, whereas in adipocytes, TRB3 upregulates fatty acid oxidation. In cultured muscle cells, TRB3 has been identified as a potential regulator of insulin signaling. However, little is known about the function and regulation of TRB3 in skeletal muscle in vivo. In the current study, we found that 4 wk of voluntary wheel running (6.6 ± 0.4 km/day) increased TRB3 mRNA by 1.6-fold and protein by 2.5-fold in the triceps muscle. Consistent with this finding, muscle-specific transgenic mice that overexpress TRB3 (TG) had a pronounced increase in exercise capacity compared with wild-type (WT) littermates (TG: 1,535 ± 283; WT: 644 ± 67 joules). The increase in exercise capacity in TRB3 TG mice was not associated with changes in glucose uptake or glycogen levels; however, these mice displayed a dramatic shift toward a more oxidative/fatigue-resistant (type I/IIA) muscle fiber type, including threefold more type I fibers in soleus muscles. Skeletal muscle from TRB3 TG mice had significantly decreased PPARα expression, twofold higher levels of miR208b and miR499, and corresponding increases in the myosin heavy chain isoforms Myh7 and Myb7b, which encode these microRNAs. These findings suggest that TRB3 regulates muscle fiber type via a peroxisome proliferator-activated receptor-α (PPAR-α)-regulated miR499/miR208b pathway, revealing a novel function for TRB3 in the regulation of skeletal muscle fiber type and exercise capacity.

scholarly journals Obesity-induced discrepancy between contractile and metabolic phenotypes in slow- and fast-twitch skeletal muscles of female obese Zucker rats

2017 ◽  
Vol 123 (1) ◽  
pp. 249-259 ◽  
Author(s):  
Luz M. Acevedo ◽  
Ana I. Raya ◽  
Rafael Ríos ◽  
Escolástico Aguilera-Tejero ◽  
José-Luis L. Rivero
Keyword(s):  
Muscle Mass ◽  
Skeletal Muscles ◽  
Fiber Type ◽  
Succinic Dehydrogenase ◽  
Zucker Rats ◽  
Fiber Types ◽  
Type Composition ◽  
Obese Zucker Rats ◽  
And Function ◽  
Fast Twitch

A clear picture of skeletal muscle adaptations to obesity and related comorbidities remains elusive. This study describes fiber-type characteristics (size, proportions, and oxidative enzyme activity) in two typical hindlimb muscles with opposite structure and function in an animal model of genetic obesity. Lesser fiber diameter, fiber-type composition, and histochemical succinic dehydrogenase activity (an oxidative marker) of muscle fiber types were assessed in slow (soleus)- and fast (tibialis cranialis)-twitch muscles of obese Zucker rats and compared with age (16 wk)- and sex (females)-matched lean Zucker rats ( n = 16/group). Muscle mass and lesser fiber diameter were lower in both muscle types of obese compared with lean animals even though body weights were increased in the obese cohort. A faster fiber-type phenotype also occurred in slow- and fast-twitch muscles of obese rats compared with lean rats. These adaptations were accompanied by a significant increment in histochemical succinic dehydrogenase activity of slow-twitch fibers in the soleus muscle and fast-twitch fiber types in the tibialis cranialis muscle. Obesity significantly increased plasma levels of proinflammatory cytokines but did not significantly affect protein levels of peroxisome proliferator-activated receptors PPARγ or PGC1α in either muscle. These data demonstrate that, in female Zucker rats, obesity induces a reduction of muscle mass in which skeletal muscles show a diminished fiber size and a faster and more oxidative phenotype. It was noteworthy that this discrepancy in muscle's contractile and metabolic features was of comparable nature and extent in muscles with different fiber-type composition and antagonist functions. NEW & NOTEWORTHY This study demonstrates a discrepancy between morphological (reduced muscle mass), contractile (shift toward a faster phenotype), and metabolic (increased mitochondrial oxidative enzyme activity) characteristics in skeletal muscles of female Zucker fatty rats. It is noteworthy that this inconsistency was comparable (in nature and extent) in muscles with different structure and function.

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