“Slow” skeletal muscles across vertebrate species

Luna, Victor M.; Daikoku, Eriko; Ono, Fumihito

doi:10.1186/s13578-015-0054-6

Cited by 28 publications

(25 citation statements)

References 53 publications

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“…Type II muscle fibers, which have less of an effect on metabolic actions of insulin than type I muscle fibers, are mostly lost as a result of age‐related muscle atrophy . However, type I muscle fibers, which exert a recognized metabolic action that increases with exercise, are significantly reduced with physical inactivity, regardless of age . In all age groups physical inactivity levels are growing fast in both developed and developing countries.…”

Section: Discussionmentioning

confidence: 99%

“…28 However, type I muscle fibers, which exert a recognized metabolic action that increases with exercise, are significantly reduced with physical inactivity, regardless of age. 29,30 In all age groups physical inactivity levels are growing fast in both developed and developing countries. In this sample, a previous study showed that 39.7% of adolescents had <2 h/wk of scheduled exercise (physical education and extracurricular sport activities).…”

Section: Discussionmentioning

confidence: 99%

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Low muscle mass is associated with cardiometabolic risk regardless of nutritional status in adolescents: A cross-sectional study in a Chilean birth cohort

et al. 2017

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Background Increased cardiometabolic risk (CMR) is documented in obese and non-obese adolescents with low muscular fitness. However, the association of low muscle mass (LMM) with CMR, independent of weight status, has not been examined. We analyzed the relationship of LMM with CMR in adolescents, regardless of their weight status. Methods Observational study in 660 adolescents. BMI, waist circumference (WC), arterial blood pressures (ABP) were measured. Total fat mass (TFM), total lean tissue (TLT) and appendicular skeletal muscle mass (ASM) were estimated (DXA). Fasting lipid profile, glucose, and insulin were measured. HOMA-IR was estimated. Metabolic Syndrome (MetS) was diagnosed (AHA/NHLBI/IDF). ROC analysis was performed to find the optimal cutoffs of TLT percentage for MetS diagnosis. Values below these cutoffs defined LMM. ANCOVA examined the association of LMM with selected cardiometabolic biomarkers. Results In both sexes, TLT showed better sensitivity and specificity than ASM for MetS diagnosis. In males and females, TLT of 66.1% and 56.3%, respectively, were the optimal cutoff for MetS diagnosis. In the sample, 17.3% of males and 23.7% of females had LMM. In both sexes, adolescents with LMM had significantly higher values of WC, ABP, TG, TC/HDL, HOMA-IR and MetS z-score than non-LMM participants. Adolescents with LMM, regardless nutritional status, had significantly increased values of MetS z-score, ABP, TG, TC/HDL-chol and HOMA-IR than non-obese non-LMM adolescents. Adolescents having both obesity and LMM had the unhealthiest CMR profile. Conclusion In adolescents, LMM was associated with higher CMR, regardless of nutritional status. In obese adolescents, LMM increased obesity-associated CMR.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Low muscle mass is associated with cardiometabolic risk regardless of nutritional status in adolescents: A cross-sectional study in a Chilean birth cohort

et al. 2017

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“…Larval zebrafish swim primarily using their axial musculature, which can generate tetanic forces between 200 and 400 mN/mm 2 (Martin et al, 2015) and tail-beat frequencies between 20 and 100 Hz (Muller & van Leeuwen, 2004). To do so, they use fast-twitch, "white" fibers that make up the bulk of the muscle mass and a superficial layer of slow, "red" fibers (Coutts, Patten, Balt, & Ali, 2006;Devoto, Melancon, Eisen, & Westerfield, 1996;Luna, Daikoku, & Ono, 2015). At faster speeds, axial motor neurons are recruited in a topographic pattern from the bottom of spinal cord up (Knafo et al, 2017;McLean, Fan, Higashijima, Hale, & Fetcho, 2007), with smaller, ventral motor neurons innervating slow muscle fibers recruited before larger, dorsal motor neurons innervating fast-twitch muscle (Menelaou & McLean, 2012;Wang & Brehm, 2017).…”

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confidence: 99%

Central and peripheral innervation patterns of defined axial motor units in larval zebrafish

Bello-Rojas

Istrate

Kishore

et al. 2019

J of Comparative Neurology

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Spinal motor neurons and the peripheral muscle fibers they innervate form discrete motor units that execute movements of varying force and speed. Subsets of spinal motor neurons also exhibit axon collaterals that influence motor output centrally. Here, we have used in vivo imaging to anatomically characterize the central and peripheral innervation patterns of axial motor units in larval zebrafish. Using early born “primary” motor neurons and their division of epaxial and hypaxial muscle into four distinct quadrants as a reference, we define three distinct types of later born “secondary” motor units. The largest is “m‐type” units, which innervate deeper fast‐twitch muscle fibers via medial nerves. Next in size are “ms‐type” secondaries, which innervate superficial fast‐twitch and slow fibers via medial and septal nerves, followed by “s‐type” units, which exclusively innervate superficial slow muscle fibers via septal nerves. All types of secondaries innervate up to four axial quadrants. Central axon collaterals are found in subsets of primaries based on soma position and predominantly in secondary fast‐twitch units (m, ms) with increasing likelihood based on number of quadrants innervated. Collaterals are labeled by synaptophysin‐tagged fluorescent proteins, but not PSD95, consistent with their output function. Also, PSD95 dendrite labeling reveals that larger motor units receive more excitatory synaptic input. Collaterals are largely restricted to the neuropil, however, perisomatic connections are observed between motor units. These observations suggest that recurrent interactions are dominated by motor neurons recruited during stronger movements and set the stage for functional investigations of recurrent motor circuitry in larval zebrafish.

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“…In larval zebrafish, both fast and slow muscle cells can contract in response to depolarizing currents [13], but only fast muscle cells are capable of firing action potentials [34, 35]. …”

Section: Resultsmentioning

confidence: 99%

A Gradient in Synaptic Strength and Plasticity among Motoneurons Provides a Peripheral Mechanism for Locomotor Control

Wang

Brehm

2017

Current Biology

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Summary The recruitment of motoneurons during force generation follows a general pattern that has been confirmed across diverse species [1–3]. Motoneurons are recruited systematically according to synaptic inputs and intrinsic cellular properties, and corresponding to movements of different intensities. However, much less is known about the output properties of individual motoneurons and how they affect the translation of motoneuron recruitment to the strength of muscle contractions. In larval zebrafish, spinal motoneurons are recruited in a topographic gradient according to their input resistance (Rin) at different swimming strengths and speeds. Whereas dorsal, lower Rin primary motoneurons (PMns) are only activated during behaviors that involve strong and fast body bends, more ventral, higher Rin secondary motoneurons (SMns) are recruited during weaker and slower movements [4–6]. Here we perform in vivo paired recordings between identified spinal motoneurons and skeletal muscle cells in larval zebrafish. We characterize individual motoneuron outputs to single muscle cells and show that the strength and reliability of motoneuron outputs are inversely correlated with motoneuron Rin. During repetitive high-frequency motoneuron drive, PMn synapses undergo depression whereas SMn synapses potentiate. We monitor muscle cell contractions elicited by single motoneurons and show that the pattern of motoneuron output strength and plasticity observed in electrophysiological recordings is reflected in muscle shortening. Our findings indicate a link between the recruitment pattern and output properties of spinal motoneurons that can together generate appropriate intensities for muscle contractions. We demonstrate that motoneuron output properties provide an additional peripheral mechanism for graded locomotor control at the neuromuscular junction.

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“Slow” skeletal muscles across vertebrate species

Cited by 28 publications

References 53 publications

Low muscle mass is associated with cardiometabolic risk regardless of nutritional status in adolescents: A cross-sectional study in a Chilean birth cohort

Low muscle mass is associated with cardiometabolic risk regardless of nutritional status in adolescents: A cross-sectional study in a Chilean birth cohort

Central and peripheral innervation patterns of defined axial motor units in larval zebrafish

A Gradient in Synaptic Strength and Plasticity among Motoneurons Provides a Peripheral Mechanism for Locomotor Control

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