The role of chronic muscle (in)activity on carnosine homeostasis: a study with spinal-cord injured athletes

2021 ◽  
Author(s):  
Kleiner Nemezio ◽  
Guilherme de Carvalho Yamaguchi ◽  
Ana Paula Boito Ramkrapes ◽  
Mariane Leichsenring Schulz ◽  
Igor Luchini Baptista ◽  
...  
Keyword(s):  
Spinal Cord ◽  
High Performance ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Type I ◽  
Shift Type ◽  
Before And After ◽  
Spinal Cord Injured ◽  
Injured Athletes

To examine the role of chronic (in)activity on muscle carnosine (MCarn) and how chronic (in)activity affects MCarn responses to β-alanine supplementation in spinal-cord injured athletes, sixteen male athletes with paraplegia were randomized (2:1 ratio) to receive β-alanine (n=11) or placebo (PL, n=5). They consumed 6.4 g‧d-1 of β-alanine or PL for 28 days. Muscle biopsies of the active deltoid and the inactive vastus lateralis (VL) were taken before and after supplementation. MCarn in the VL was also compared with the VL of a group of individuals without paraplegia (n=15). MCarn was quantified in whole muscle and in pools of individual fibers by High-performance Liquid Chromatography. MCarn was higher in chronically inactive VL vs. well-trained deltoid (32.0±12.0 vs. 20.5±6.1 mmol‧kg-1 DM; p=0.018). MCarn was higher in inactive vs. active VL (32.0±12.0 vs. 21.2±7.5 mmol‧kg-1 DM; p=0.011). In type-I fibers, MCarn was significantly higher in the inactive VL than in the active deltoid (38.3±4.7 vs. 27.3±11.8 mmol‧kg-1 DM, p=0.014). MCarn increased similarly between inactive VL and active deltoid in the β-alanine group (VL: 68.9±55.1%, p=0.0002; deltoid: 90.5±51.4%, p<0.0001), with no changes in the PL group. MCarn content was higher in the inactive VL than in the active deltoid and the active VL, but this is probably a consequence of fiber type shift (type I to type II) that occurs with chronic inactivity. Chronically inactive muscle showed an increase in MCarn after BA supplementation equally to the active muscle, suggesting that carnosine accretion following β-alanine supplementation is not influenced by muscle inactivity.

Human and Rat Skeletal Muscle Adaptations to Spinal Cord Injury

2003 ◽  
Vol 28 (3) ◽  
pp. 491-500 ◽  
Author(s):  
Chris M. Gregory ◽  
Krista Vandenborne ◽  
Michael J. Castro ◽  
G. Alton Dudley
Keyword(s):  
Skeletal Muscle ◽  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Type I ◽  
Glycerol Phosphate ◽  
Cross Sectional ◽  
Muscle Plasticity ◽  
Cord Injury

Results of studies of rodent skeletal muscle plasticity are often extrapolated to humans. However, responses to "disuse" may be species specific, in part because of different inherent properties of anatomically similar muscles. Thus, this study quantified human and rat m. vastus lateralis (VL) fiber adaptations to 11 weeks of spinal cord injury (SCI). The m. VL was taken from 8 young (54 d) male Charles River rats after T-9 laminectomy (n = 4) or sham surgery (n = 4). In addition, the m. VL was biopsied in 7 able-bodied and in 7 SCI humans (31.3 ± 4.7 years, mean ± SE). Samples were sectioned and fibers were analyzed for type (I, IIa, IIb/x), cross-sectional area (CSA), succinate dehydrogenase (SDH), α-glycerol-phosphate dehydrogenase (GPDH), and actomyosin adenosine triphosphatase (qATPase) activities. Rat fibers had 1.5- to 2-fold greater SDH and GPDH activities while their fibers were 60% the size of those in humans. The most striking differences, however, were the absence of slow fibers in the rat and its four-fold greater proportion of IIb/x fibers (80% vs. 16% of the CSA) compared to humans. SCI decreased SDH activity more in rats whereas atrophy and IIa to IIb/x fiber shift occurred to a greater extent in humans. It is suggested that the rat is a reasonable model for studying the predominant response to SCI, atrophy. However, its high proportion of IIb/x fibers limits evaluation of the mechanical consequences of shifting to "faster" contractile machinery after SCI. Key words: enzyme, fiber type, disuse, biopsy

Determination of the speed-time relationship during handcycling in spinal cord injured athletes

2021 ◽  
pp. 1-8
Author(s):  
Diego Antunes ◽  
Eduardo Marcel Fernandes Nascimento ◽  
Gary Brickley ◽  
Gabriela Fischer ◽  
Ricardo Dantas de Lucas
Keyword(s):  
Spinal Cord ◽  
Time Relationship ◽  
Spinal Cord Injured ◽  
Injured Athletes

MSC secreted extracellular vesicles carrying TGF-beta upregulate Smad 6 expression and promote the regrowth of neurons in spinal cord injured rats

2021 ◽  
Author(s):  
Tianyu Han ◽  
Peiwen Song ◽  
Zuomeng Wu ◽  
Xiang Xia ◽  
Ying Wang ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Stem Cells ◽  
Extracellular Vesicles ◽  
Kinase Inhibitor ◽  
Inflammatory Factors ◽  
Type I ◽  
Post Injury ◽  
Cord Injury ◽  
Spinal Cord Injured ◽  
Feedback Regulator

Abstract Mesenchymal stem cells (MSCs) are a promising therapy for spinal cord injury (SCI) as they can provide a favorable environment for the regrowth of neurons and axons by inhibiting receptor-regulated Smads (R-Smads) in endogenous neural stem cells (NSCs). However, their mechanism of action and effect on the expression of inhibitory Smads (I-Smads) remains unclear. Here, we demonstrated that Extracellular vesicles (EVs) from MSCs were able to upregulate the Smad 6 expression by carrying TGF-β. Smad 6 knockdown in NSCs partly weakened the BMSC-EVs-induced effect on neural differentiation. In spinal cord injured rats, we found that in the acute phase of injury, the Smad 6 expression was not reduced by the treatment of TGF-β type I receptor kinase inhibitor SB431542, indicating that the Smad 6 expression was not only mediated TGF-β, the inflammatory factors and BMPs were also involved. However, in the later phase of SCI, the Smad 6 expression was reduced by the addition of SB 431542, suggesting in this phase, TGF-β played a key role on the mediation of Smad 6 expression. In addition, by immunohistochemistry staining, Hematoxylin-eosin staining and BBB scores, we revealed that the early inhibition of TGF-β did not increase the regrowth of neurons. Instead, it increased the volume of cavity and the Caspase-3 expression at 24h post-injury, leading to a wore functional outcome. In contrast the later treatment of the TGF-β inhibitor promoted the regrowth of neurons around the cavity, resulting into a better neurological outcome. Together all these results indicated that Smad 6 acts as a feedback regulator to prevents over-differentiation of NSCs to astrocytes and BMSC-EVs can upregulate Smad 6 expression by the carring TGF-β.

In vitro human masseter muscle hypersensitivity: a possible explanation for increase in masseter tone

1996 ◽  
Vol 80 (5) ◽  
pp. 1547-1553 ◽  
Author(s):  
P. J. Adnet ◽  
H. Reyford ◽  
B. M. Tavernier ◽  
T. Etchrivi ◽  
I. Krivosic ◽  
...  
Keyword(s):  
Masseter Muscle ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Threshold Concentration ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Cross Sectional ◽  
Significant Difference ◽  
Maximal Tension

To determine whether a difference in fiber-type caffeine and Ca2+ sensitivities exists between human masseter and vastus lateralis skeletal muscle, we compared the fiber-type caffeine sensitivities in chemically skinned muscle fibers from 13 masseter and 18 vastus lateralis muscles. Caffeine sensitivity was defined as the threshold concentration inducing > 10% of the maximal tension obtained after the fiber was loaded with a 1.6 x 10(-2) mM Ca2+ solution for 30 s. Significant difference in the mean caffeine sensitivity was found between type I masseter fibers [2.57 +/- 1.32 (SD) mM] vs. type I (6.02 +/- 1.74 mM) and type II vastus lateralis fibers (11.25 +/- 3.13 mM). Maximal Ca(2+)-activated force per cross-sectional area was significantly different between masseter and vastus lateralis fibers. However, the Ca2+ concentration corresponding to half-maximal tension (pCa50) was not significantly different between type I masseter (pCa50 5.9 +/- 0.02) and type I vastus lateralis muscle (pCa50 6.01 +/- 0.08). These results suggest that the increase in caffeine sensitivity of masseter muscle reflects the presence of a low reactivity threshold of the sarcoplasmic reticulum.

Carnitine metabolism in human muscle fiber types during submaximal dynamic exercise

1996 ◽  
Vol 80 (3) ◽  
pp. 1061-1064 ◽  
Author(s):  
D. Constantin-Teodosiu ◽  
S. Howell ◽  
P. L. Greenhaff
Keyword(s):  
Muscle Fiber ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Group Formation ◽  
Free Carnitine ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Carnitine Metabolism ◽  
Type I Fibers

The effect of prolonged exhaustive exercise on free carnitine and acetylcarnitine concentrations in mixed-fiber skeletal muscle and in type I and II muscle fibers was investigated in humans. Needle biopsy samples were obtained from the vastus lateralis of six subjects immediately after exhaustive one-legged cycling at approximately 75% of maximal O2 uptake from both the exercised and nonexercised (control) legs. In the resting (control) leg, there was no difference in the free carnitine concentration between type I and II fibers (20.36 +/- 1.25 and 20.51 +/- 1.16 mmol/kg dry muscle, respectively) despite the greater potential for fat oxidation in type I fibers. However, the acetylcarnitine concentration was slightly greater in type I fibers (P < 0.01). During exercise, acetylcarnitine accumulation occurred in both muscle fiber types, but accumulation was greatest in type I fibers (P < 0.005). Correspondingly, the concentration of free carnitine was significantly lower in type I fibers at the end of exercise (P < 0.001). The sum of free carnitine and acetylcarnitine concentrations in type I and II fibers at rest was similar and was unchanged by exercise. In conclusion, the findings of the present study support the suggestion that carnitine buffers excess acetyl group formation during exercise and that this occurs in both type I and II fibers. However, the greater accumulation of acetylcarnitine in type I fibers during prolonged exercise probably reflects the greater mitochondrial content of this fiber type.

Effect of weight loss on muscle lipid content in morbidly obese subjects

2003 ◽  
Vol 284 (4) ◽  
pp. E726-E732 ◽  
Author(s):  
Robert E. Gray ◽  
Charles J. Tanner ◽  
Walter J. Pories ◽  
Kenneth G. MacDonald ◽  
Joseph A. Houmard
Keyword(s):  
Weight Loss ◽  
Insulin Action ◽  
Fiber Type ◽  
Gastric Bypass Surgery ◽  
Morbidly Obese ◽  
Type I ◽  
Fiber Types ◽  
Model Assessment ◽  
Before And After ◽  
Obese Subjects

The purpose of this study was to test the hypothesis that weight loss results in a reduction in intramuscular lipid (IMCL) content that is concomitant with enhanced insulin action. Muscle biopsies were obtained from morbidly obese individuals [body mass index (BMI) 52.2 ± 2.5 kg/m2; n= 6] before and after gastric bypass surgery, an intervention that improves insulin action. With intervention, there was a 47% reduction ( P < 0.01) in BMI and a 93% decrease in homeostasis model assessment, or HOMA (7.0 ± 1.9 vs. 0.5 ± 0.1). Histochemically determined IMCL content decreased ( P < 0.05) by ∼30%. In relation to fiber type, IMCL was significantly higher in type I vs. type II fibers. In both fiber types, there were reductions in IMCL and trends for muscle atrophy. Despite these two negating factors, the IMCL-to-fiber area ratio still decreased by ∼44% with weight loss. In conclusion, despite differing initial levels and possible atrophy, weight loss appears to decrease IMCL deposition to a similar relative extent in type I and II muscle fibers. This reduction in intramuscular triglyceride may contribute to enhanced insulin action seen with weight loss.

scholarly journals The role of the mucosa in modulation of evoked responses in the spinal cord injured rat bladder

2018 ◽  
Vol 37 (5) ◽  
pp. 1583-1593 ◽  
Author(s):  
Claire Doyle ◽  
Vivian Cristofaro ◽  
Bryan S. Sack ◽  
Fabliha Mahmood ◽  
Maryrose P. Sullivan ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Evoked Responses ◽  
Rat Bladder ◽  
Spinal Cord Injured

Leptin response to short-term fasting in sympathectomized men: role of the SNS

2003 ◽  
Vol 284 (3) ◽  
pp. E634-E640 ◽  
Author(s):  
Justin Y. Jeon ◽  
Vicki J. Harber ◽  
Robert D. Steadward
Keyword(s):  
Body Mass Index ◽  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Nervous System ◽  
Short Term ◽  
Cord Injury ◽  
Before And After ◽  
Sympathetic Nervous ◽  
Plasma Leptin

We studied plasma leptin levels in six people with high-lesion spinal cord injury [SCI; body mass index (BMI) 25.9 ± 1.5 kg/m2, age 37 ± 3.0 yr] and six able-bodied (AB) controls (BMI 29.1 ± 1.9 kg/m2, age 35 ± 3.5 yr) before and after 12, 24, and 36 h of fasting. The plasma leptin levels significantly decreased during 36 h fasting by 48.8 ± 4.5% (pre: 11.3 ± 2.3, post: 6.2 ± 1.5 ng/ml) and 38.6 ± 7.9% (pre: 7.6 ± 5.0, post: 4.2 ± 1.0 ng/ml) in SCI and AB, respectively. Plasma leptin started to decrease at 24 h of fasting in the SCI group, whereas plasma leptin started to decrease at 12 h of fasting in the AB group. The current study demonstrated that plasma leptin decreased with fasting in both SCI and AB groups, with the leptin decrease being delayed in the SCI group. The delayed leptin response to fasting in the SCI group may be because of increased fat mass (%body fat, SCI: 33.8 ± 3.0, AB: 24.1 ± 2.9) and sympathetic nervous system dysfunction.

scholarly journals Prolonged C2 spinal hemisection-induced inactivity reduces diaphragm muscle specific force with modest, selective atrophy of type IIx and/or IIb fibers

2013 ◽  
Vol 114 (3) ◽  
pp. 380-386 ◽  
Author(s):  
Carlos B. Mantilla ◽  
Sarah M. Greising ◽  
Wen-Zhi Zhan ◽  
Yasin B. Seven ◽  
Gary C. Sieck
Keyword(s):  
Spinal Cord ◽  
Muscle Fiber ◽  
Fiber Type ◽  
Diaphragm Muscle ◽  
Emg Activity ◽  
Type I ◽  
Specific Force ◽  
Type Distribution ◽  
Fiber Size ◽  
Fiber Type Distribution

The diaphragm muscle (DIAm) is critically responsible for sustaining ventilation. Previously we showed in a commonly used model of spinal cord injury, unilateral spinal cord hemisection at C2 (SH), that there are minimal changes to muscle fiber cross-sectional area (CSA) and fiber type distribution following 14 days of SH-induced ipsilateral DIAm inactivity. In the present study, effects of long-term SH-induced inactivity on DIAm fiber size and force were examined. We hypothesized that prolonged inactivity would not result in substantial DIAm atrophy or force loss. Adult rats were randomized to control or SH groups ( n = 34 total). Chronic bilateral DIAm electromyographic (EMG) activity was monitored during resting breathing. Minimal levels of spontaneous recovery of ipsilateral DIAm EMG activity were evident in 42% of SH rats (<25% of preinjury root mean square amplitude). Following 42 days of SH, DIAm specific force was reduced 39%. There was no difference in CSA for type I or IIa DIAm fibers in SH rats compared with age, weight-matched controls (classification based on myosin heavy chain isoform expression). Type IIx and/or IIb DIAm fibers displayed a modest 20% reduction in CSA ( P < 0.05). Overall, there were no differences in the distribution of fiber types or the contribution of each fiber type to the total DIAm CSA. These data indicate that reduced specific force following prolonged inactivity of the DIAm is associated with modest, fiber type selective adaptations in muscle fiber size and fiber type distribution.

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