slow and fast twitch muscle fibers and activity

Unloading of slow-twitch muscles results in increased muscle fatigue and the mechanisms of this effect are poorly studied. We aimed to analyze the role of high-energy phosphates accumulation during the first week of rat hindlimb suspension plays in a fiber-type phenotype shift towards fast-type fatigable muscle fibers. Male Wistar rats were divided into 3 groups (n = 8): C - vivarium control; 7HS - 7-day hindlimb suspension; 7HB - 7-day hindlimb suspension with intraperitoneal injection of beta-guanidine propionic acid (β-GPA, 400 mg/kg b w)...

Guilu Erxian Jiao (GEJ) is a commonly used nutritional supplement due to its rich content of amino acids. It is also a traditional herbal medicine for improving degenerative joint. This study aimed to investigate the effect and mechanism of GEJ water extract (GEJ-WE) on skeletal muscle in C2C12 myotubes and C57BL/6J mice. Analysis of GEJ-WE were performed by high-performance liquid chromatography fingerprinting with chemical standards. Protein expression, mRNA level, glycogen content, mitochondria activity and ATP level were evaluated by western blots, real-time PCR, PAS staining, MTT and ATP bioluminescence assay, respectively...

Skeletal muscle consists of both fast- and slow-twitch fibers. Phospholipids are important structural components of cellular membranes, and the diversity of their fatty acid composition affects membrane fluidity and permeability. Although some studies have shown that acyl chain species in phospholipids differ among various muscle fiber types, the mechanisms underlying these differences are unclear. To investigate this, we analyzed phosphatidylcholine (PC) and phosphatidylethanolamine (PE) molecules in the murine extensor digitorum longus (EDL; fast-twitch) and soleus (slow-twitch) muscles...

MicroRNAs (miRNAs) are a class of non-coding single-stranded RNA molecules about 22 nucleotides in length and are encoded by endogenous genes, and are involved in the regulation of post-transcriptional gene expression in animals and plants. Many studies have shown that microRNAs regulate the development of skeletal muscle, mainly manifested in the activation of muscle satellite cells and biological processes such as proliferation, differentiation, and formation of muscle tubes. In this study, miRNA sequencing screening of longissimus dorsi (LD, mainly fast-twitch fibers) and soleus muscle (Sol, dominated by slow-twitch fibers) identified the miR-196b-5p as a differentially expressed and highly conserved sequence in different skeletal muscles...

Currently, no ideal treatment exists to combat skeletal muscle disuse-induced atrophy and loss of strength. Because the activity of AMP-activated protein kinase (AMPK) in rat soleus muscle is suppressed at the early stages of disuse, we hypothesized that pre-treatment of rats with metformin (an AMPK activator) would exert beneficial effects on skeletal muscle during disuse. Muscle disuse was performed via hindlimb suspension (HS). Wistar rats were divided into four groups: (1) control (C), (2) control + metformin for 10 days (C+Met), (3) HS for 7 days (HS), (4) metformin treatment for 7 days before HS and during the first 3 days of 1-week HS (HS+Met)...

Skeletal muscle is highly developed after birth, consisting of glycolytic fast-twitch and oxidative slow-twitch fibers; however, the mechanisms of fiber-type-specific differentiation are poorly understood. Here, we found an unexpected role of mitochondrial fission in the differentiation of fast-twitch oxidative fibers. Depletion of the mitochondrial fission factor dynamin-related protein 1 (Drp1) in mouse skeletal muscle and cultured myotubes results in specific reduction of fast-twitch muscle fibers independent of respiratory function...

INTRODUCTION: Skeletal muscle insulin resistance (IR) plays an important role in the pathogenesis of type 2 diabetes mellitus. Skeletal muscle is a heterogeneous tissue composed of different muscle fiber types that contribute distinctly to IR development. Glucose transport shows more protection in slow-twitch muscles than in fast-twitch muscles during IR development, while the mechanisms involved remain unclear. Therefore, we investigated the role of the mitochondrial unfolded protein response (UPRmt) in the distinct resistance of two types of muscle in IR...

The mechanisms underlying cigarette smoke-induced mitochondrial dysfunction in skeletal muscle are still poorly understood. Accordingly, this study aimed to examine the effects of cigarette smoke on mitochondrial energy transfer in permeabilized muscle fibers from skeletal muscles with differing metabolic characteristics. The electron transport chain (ETC) capacity, ADP transport, and respiratory control by ADP were assessed in fast- and slow-twitch muscle fibers from C57BL/6 mice (n = 11) acutely exposed to cigarette smoke concentrate (CSC) using high-resolution respirometry...

The conversion of skeletal muscle fiber from fast-twitch to slow-twitch is crucial for sustained contractile and stretchable events, energy homeostasis, and anti-fatigue ability. The purpose of our study was to explore the mechanism and effects of garcinol on the regulation of skeletal muscle fiber type transformation. Forty 21-day-old male C57/BL6J mice (n = 10/diet) were fed a control diet or a control diet plus garcinol at 100 mg/kg (Low Gar), 300 mg/kg (Mid Gar), or 500 mg/kg (High Gar) for 12 weeks. The tibialis anterior (TA) and soleus muscles were collected for protein and immunoprecipitation analyses...

BACKGROUND: Skeletal muscle is comprised of heterogeneous myofibers that differ in their physiological and metabolic parameters. Of these, slow-twitch (type I; oxidative) myofibers have more myoglobin, more mitochondria, and higher activity of oxidative metabolic enzymes compared to fast-twitch (type II; glycolytic) myofibers. METHODS: In our previous study, we found a novel LncRNA-TBP (for "LncRNA directly binds TBP transcription factor") is specifically enriched in the soleus (which has a higher proportion of slow myofibers)...

BACKGROUND: Adolescent idiopathic scoliosis (AIS) refers to a three-dimensional spinal deformity which has a typical onset during adolescence. In most cases, the cause of the deformity cannot be clearly identified. Unbalanced paraspinal muscle activity in AIS patients was reported and hypoxia was implicated to regulate myogenesis. This study aims to investigate the association between myogenesis/muscle toning and HIF-αs activity in the pathogenesis of AIS. METHODS: HIF-αs expression was examined by enzyme-linked immunosorbent assay and western blot in paraspinal myoblasts isolated from 18 subjects who underwent deformity correction surgery...

Muscle fiber composition is associated with physical performance, with endurance athletes having a high proportion of slow-twitch muscle fibers compared to power athletes. Approximately 45% of muscle fiber composition is heritable, however, single nucleotide polymorphisms (SNP) underlying inter-individual differences in muscle fiber types remain largely unknown. Based on three whole genome SNP datasets, we have shown that the rs236448 A allele located near the cyclin-dependent kinase inhibitor 1A (CDKN1A) gene was associated with an increased proportion of slow-twitch muscle fibers in Russian (n = 151; p = 0...

BACKGROUND: This experiment aimed to investigate effects of dietary L-theanine supplementation on pork quality and muscle fiber type transformation in finishing pigs. In a 30-day experiment, 18 healthy Duroc × Landrace × Yorkshire (DLY) pigs with an average body weight of 86.03 ± 0.83 kg were randomly divided into three groups (a basal diet or a basal diet supplemented with 500 and 1000 ppm L-theanine, respectively), with six duplicates and one pig per replicate...

OBJECTIVES: Irisin, a novel myokine that responds to exercise, was initially identified as a regulator of fat tissue metabolism. We aimed to investigate fibronectin type III domain-containing protein 5 (Fndc5)/irisin, auto/para-crine role in different muscle fibers, different activities, and muscle cell differentiation. METHODS: Using in-vitro , ex-vivo , and in-vivo muscle models, Fndc5 was studied at the physiological and molecular levels. RESULTS: Following training, C57BL/6 mice (n=10) were subject to fast and slow-twitch muscles dissection and molecular analysis...

Fast-twitch muscle and slow-twitch muscle are optimized for strong, short duration contractions and for tonic postural activity respectively. Structural events (OFF to ON transitions) in the myosin containing thick filaments in fast muscle help determine the timing and strength of contractions but these have not been studied in slow-twitch muscle. The X-ray diffraction signatures of structural OFF to ON transitions are different in fast extensor digitorum longus (EDL) and slow soleus (SOL) muscle, being completely absent during twitches in soleus muscle and blunted during tetanic contractions SOL as compared to EDL Quasi-stepwise thick filament structural OFF to ON transitions in fast twitch muscle may be an adaptation for rapid, ballistic movements whereas more graded OFF to ON structural transitions in slow-twitch muscle may be an adaptation for slower, finer motions...

Skeletal muscle adaptations to exercise have been associated with a range of health-related benefits, but cell type-specific adaptations within the muscle are incompletely understood. Here we use single-cell sequencing to determine the effects of exercise on cellular composition and cell type-specific processes in human skeletal muscle before and after intense exercise. Fifteen clusters originating from six different cell populations were identified. Most cell populations remained quantitatively stable after exercise, but a large transcriptional response was observed in mesenchymal, endothelial, and myogenic cells, suggesting that these cells are specifically involved in skeletal muscle remodeling...

Lorises are a group of globally threatened strepsirrhine primates that exhibit many unusual physiological and behavioral features, including a low metabolic rate, slow movement, and hibernation. Here, we assembled a chromosome-level genome sequence of the pygmy loris ( Xanthonycticebus pygmaeus ) and resequenced whole genomes from 50 pygmy lorises and 6 Bengal slow lorises ( Nycticebus bengalensis ). We found that many gene families involved in detoxification have been specifically expanded in the pygmy loris, including the GSTA gene family, with many newly derived copies functioning specifically in the liver...

Skeletal muscle fiber types can contribute in part to affecting pork quality parameters. Biceps femoris (Bf) (fast muscle or white muscle) and Soleus (Sol) (slow muscle or red muscle) are two typical skeletal muscles characterized by obvious muscle fiber type differences in pigs. However, the critical proteins and potential regulatory mechanisms regulating porcine skeletal muscle fibers have yet to be clearly defined. In this study, the isobaric Tag for Relative and Absolute Quantification (iTRAQ)-based proteome was used to identify the key proteins affecting the skeletal muscle fiber types with Bf and Sol, by integrating the previous transcriptome data, while function enrichment analysis and a protein-protein interaction (PPI) network were utilized to explore the potential regulatory mechanisms of skeletal muscle fibers...

PURPOSE: This study evaluated how extended match time (90 + 30 min) affected physiological responses and fatigue in male soccer players. METHODS: Twenty competitive players (age 21 ± 2 [±SD] years; VO2max 59 ± 4 ml/min/kg) completed an experimental match with their activity pattern and HR assessed throughout the game, while countermovement jump (CMJ) performance and repeated sprint ability (RSA) were tested and quadriceps muscle biopsies and venous blood samples taken at baseline and after 90 and 120 min of match-play...

Ellagic acid (EA), because of its remarkable health-promoting ability, has aroused widespread interest in the fields of nutrition and medicine. However, no reports showed that EA regulates mitochondrial biogenesis as well as muscle fiber-type composition in pigs. Our study found that dietary 75 and 150 mg/kg EA obviously augmented the slow myosin heavy chain (MyHC) protein level, the number of slow-twitch muscle fibers, and the activity of malate dehydrogenase (MDH) in the longissimus thoracis (LT) muscle of growing-finishing pigs...