myofibrillar hypertrophy

Alpha-B-crystallin, a member of the small heat shock family of proteins, has been implicated in a variety of cardiomyopathies and in normal cardiac homeostasis. It is known to function as a molecular chaperone, particularly for desmin, but also interacts with a wide variety of additional proteins. The molecular chaperone function is also enhanced by signal-dependent phosphorylation at specific residues under stress conditions. Naturally occurring mutations in CRYAB , the gene that encodes alpha-B-crystallin, have been suggested to alter ionic intermolecular interactions that affect dimerization and chaperone function...

In order to determine the behavior of the right ventricle, we have reviewed the existing literature in the area of cardiac remodeling, signal transduction pathways, subcellular mechanisms, β-adrenoreceptor-adenylyl cyclase system and myocardial catecholamine content during the development of left ventricular failure due to myocardial infarction. The right ventricle exhibited adaptive cardiac hypertrophy due to increases in different signal transduction pathways involving the activation of protein kinase C, phospholipase C and protein kinase A systems by elevated levels of vasoactive hormones such as catecholamines and angiotensin II in the circulation at early and moderate stages of heart failure...

Blood flow restriction applied during low-load resistance training (LL-BFR) induces a similar increase in the cross-sectional area of muscle fibers (fCSA) compared to traditional high-load resistance training (HL-RT). However, it is unclear whether LL-BFR leads to differential changes in myofibrillar spacing in muscle fibers and/or extracellular area compared to HL-RT. Therefore, this study aimed to investigate whether the hypertrophy of type I and II fibers induced by LL-BFR or HL-RT is accompanied by differential changes in myofibrillar and non-myofibrillar areas...

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is the most prevalent monogenic heart disorder. However, the pathogenesis of HCM, especially its nongenetic mechanisms, remains largely unclear. Transcription factors are known to be involved in various biological processes including cell growth. We hypothesized that SP1 (specificity protein 1), the first purified TF in mammals, plays a role in the cardiomyocyte growth and cardiac hypertrophy of HCM. METHODS: Cardiac-specific conditional knockout of Sp1 mice were constructed to investigate the role of SP1 in the heart...

BACKGROUND: Surgery for urological cancers is associated with high complication rates and survivors commonly experience fatigue, reduced physical ability and quality of life. High-intensity interval training (HIIT) as surgical prehabilitation has been proven effective for improving the cardiorespiratory fitness (CRF) of urological cancer patients, however the mechanistic basis of this favourable adaptation is undefined. Thus, we aimed to assess the mechanisms of physiological responses to HIIT as surgical prehabilitation for urological cancer...

Obesity and type 2 diabetes are at epidemic levels and a significant proportion of these patients are diagnosed with left ventricular hypertrophy. CREB R egulated T ranscription C o-activator ( CRTC ) is a key regulator of metabolism in mammalian hepatocytes, where it is activated by calcineurin (CaN) to increase expression of gluconeogenic genes. CaN is known its role in pathological cardiac hypertrophy, however, a role for CRTC in the heart has not been identified. In Drosophila , CRTC null mutants have little body fat and exhibit severe cardiac restriction, myofibrillar disorganization, cardiac fibrosis and tachycardia, all hallmarks of heart disease...

PURPOSE: Skeletal muscle regulates health and performance by maintaining or increasing strength and muscle mass. Although the molecular mechanisms in response to resistance exercise (RE) significantly target the activation of protein synthesis, a plethora of other mechanisms and structures must be involved in orchestrating the communication, repair, and restoration of homeostasis after RE stimulation. In practice, RE can be modulated by variations in intensity, continuity and volume, which affect molecular responses and skeletal muscle adaptation...

Despite the identification of numerous molecular pathways modulating cardiac hypertrophy its pathogenesis is not completely understood. In this study we define an unexpected role for Fibin ("fin bud initiation factor homolog") in cardiomyocyte hypertrophy. Via gene expression profiling in hypertrophic murine hearts after transverse aortic constriction we found a significant induction of Fibin. Moreover, Fibin was upregulated in another mouse model of cardiac hypertrophy (calcineurin-transgenics) as well as in patients with dilated cardiomyopathy...

In chickens, muscle development during embryonic growth is predominantly by myofiber hyperplasia. Following hatch, muscle growth primarily occurs via hypertrophy of the existing myofibers. Since myofiber number is set at hatch, production of more muscle fibers during embryonic growth would provide a greater myofiber number at hatch and potential for posthatch muscle growth by hypertrophy. Therefore, to improve performance in broilers, this study investigated the effect of in ovo spray application of probiotics on overall morphometry and muscle development in broiler embryos...

Insulin-like growth factor-1 (Igf1) regulates skeletal muscle growth in fishes by increasing protein synthesis and promoting muscle hypertrophy. When fish experience periods of insufficient food intake, they undergo slower muscle growth or even muscle wasting, and those changes emerge in part from nutritional modulation of Igf1 signaling. Here, we examined how food deprivation (fasting) affects Igf1 regulation of liver and skeletal muscle gene expression in gopher rockfish (Sebastes carnatus), a nearshore rockfish of importance for commercial and recreational fisheries in the northeastern Pacific Ocean, to understand how food limitation impacts Igf regulation of muscle growth pathways...

Low-load blood flow-restricted resistance exercise (BFRRE) constitutes an effective means to produce skeletal muscle hypertrophy. Nonetheless, its applicability to counteract the age-related skeletal muscle decay at a cellular level, is not clear. Therefore, we investigated the effect of BFRRE on muscle fiber morphology, integrated muscle protein synthesis, muscle stem cells (MuSCs), myonuclear content, and muscle functional capacity in healthy older individuals. Twenty-three participants with a mean age of 66 yr (56-75 yr) were randomized to 6 wk of supervised BFRRE (3 sessions per week) or non-exercise control (CON)...

BACKGROUND: It remains unclear whether non-animal-derived dietary protein sources (and therefore vegan diets) can support resistance training-induced skeletal muscle remodeling to the same extent as animal-derived protein sources. METHODS: In phase 1, 16 healthy young adults (m = 8, f = 8; age: 23 ± 1 y; BMI: 23 ± 1 kg/m2 ) completed a 3-d dietary intervention (high protein, 1.8 g·kg bm-1 ·d-1 ) where protein was derived from omnivorous (OMNI1; n = 8) or exclusively nonanimal (VEG1; n = 8) sources, alongside daily unilateral leg resistance exercise...

BACKGROUND: Tissue organoids generated from human pluripotent stem cells are valuable tools for disease modelling and to understand developmental processes. While recent progress in human cardiac organoids revealed the ability of these stem cell-derived organoids to self-organize and intrinsically formed chamber-like structure containing a central cavity, it remained unclear the processes involved that enabled such chamber formation. METHODS: Chambered cardiac organoids (CCOs) differentiated from human embryonic stem cells (H7) were generated by modulation of Wnt/ß-catenin signalling under fully defined conditions, and several growth factors essential for cardiac progenitor expansion...

Genetic variants in α-actinin-2 (ACTN2) are associated with several forms of (cardio)myopathy. We previously reported a heterozygous missense (c.740C>T) ACTN2 gene variant, associated with hypertrophic cardiomyopathy, and characterized by an electro-mechanical phenotype in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Here, we created with CRISPR/Cas9 genetic tools two heterozygous functional knock-out hiPSC lines with a second wild-type (ACTN2wt) and missense ACTN2 (ACTN2mut) allele, respectively...

AIMS: To test the hypothesis that the activation of the growth hormone-releasing hormone (GHRH) receptor signaling pathway within the myocardium both prevents and reverses diastolic dysfunction and pathophysiologic features consistent with heart failure with preserved ejection fraction (HFpEF). Impaired myocardial relaxation, fibrosis and ventricular stiffness, among other multi-organ morbidities, characterize the phenotype underlying the HFpEF syndrome. Despite the rapidly increasing prevalence of HFpEF, few effective therapies have emerged...

We evaluated the effects of higher-load (HL) versus (lower-load) higher-volume (HV) resistance training on skeletal muscle hypertrophy, strength, and muscle-level molecular adaptations. Trained men ( n  = 15, age: 23 ± 3 years; training experience: 7 ± 3 years) performed unilateral lower-body training for 6 weeks (3× weekly), where single legs were randomly assigned to HV and HL paradigms. Vastus lateralis (VL) biopsies were obtained prior to study initiation (PRE) as well as 3 days (POST) and 10 days following the last training bout (POSTPR)...

BACKGROUND: Abnormalities in cardiac energy metabolism occur in heart failure (HF) and contribute to contractile dysfunction, but their role, if any, in HF-related pathologic remodeling is much less established. CK (creatine kinase), the primary muscle energy reserve reaction which rapidly provides ATP at the myofibrils and regenerates mitochondrial ADP, is down-regulated in experimental and human HF. We tested the hypotheses that pathologic remodeling in human HF is related to impaired cardiac CK energy metabolism and that rescuing CK attenuates maladaptive hypertrophy in experimental HF...

Generally, skeletal muscle adaptations to exercise are perceived through a dichotomous lens where the metabolic stress imposed by aerobic training leads to increased mitochondrial adaptations while the mechanical tension from resistance training leads to myofibrillar adaptations. However, there is emerging evidence for cross over between modalities where aerobic training stimulates traditional adaptations to resistance training (e.g., hypertrophy) and resistance training stimulates traditional adaptations to aerobic training (e...

PURPOSE: Resistance training induces skeletal muscle hypertrophy via the summated effects of post-exercise elevations in myofibrillar protein synthesis (MyoPS) that persist for up to 48 h, although research in females is currently lacking. MyoPS is regulated by mTOR translocation and colocalization; however, the effects of resistance training on these intracellular processes is unknown. We hypothesized that MyoPS would correlate with hypertrophy only after training in both sexes and would be associated with intracellular redistribution of mTOR...

Factors underpinning the time-course of resistance-type exercise training (RET) adaptations are not fully understood. This study hypothesized that consuming a twice-daily protein-polyphenol beverage (PPB; n = 15; age, 24 ± 1 yr; BMI, 22.3 ± 0.7 kg·m-2 ) previously shown to accelerate recovery from muscle damage and increase daily myofibrillar protein synthesis (MyoPS) rates would accelerate early (10 sessions) improvements in muscle function and potentiate quadriceps volume and muscle fiber cross-sectional area (fCSA) following 30 unilateral RET sessions in healthy, recreationally active, adults...