Vav2 catalysis-dependent pathways contribute to skeletal muscle growth and metabolic homeostasis

Remodeling p38 signaling in muscle controls locomotor activity via IL-15

Skeletal muscle has gained recognition as an endocrine organ releasing myokines upon contraction during physical exercise. These myokines exert both local and pleiotropic health benefits, underscoring the crucial role of muscle function in countering obesity and contributing to the overall positive effects of exercise on health. Here, we found that exercise activates muscle p38γ, increasing locomotor activity through the secretion of interleukin-15 (IL-15). IL-15 signals in the motor cortex, stimulating locomotor activity. This activation of muscle p38γ, leading to an increase locomotor activity, plays a crucial role in reducing the risk of diabetes and liver steatosis, unveiling a vital muscle-brain communication pathway with profound clinical implications. The correlation between p38γ activation in human muscle during acute exercise and increased blood IL-15 levels highlights the potential therapeutic relevance of this pathway in treating obesity and metabolic diseases. These findings provide valuable insights into the molecular basis of exercise-induced myokine responses promoting physical activity.

Serum protein and imaging biomarkers after intermittent steroid treatment in muscular dystrophy

Background

Weekly Steroids in Muscular Dystrophy (WSiMD) was a pilot study to evaluate once weekly prednisone in patients with Limb Girdle and Becker muscular dystrophy (LGMD and BMD, respectively). At study endpoint, there were trends towards increased lean mass, reduced fat mass, reduced creatine kinase and improved motor function. The investigation was motivated by studies in mouse muscular dystrophy models in which once weekly glucocorticoid exposure enhanced muscle strength and reduced fibrosis.

Methods

WSiMD participants provided blood samples for aptamer serum profiling at baseline and after 6 months of weekly steroids. A subset completed magnetic resonance (MR) evaluation of muscle at study onset and endpoint.

Results/Conclusions

At baseline compared to age and sex-matched healthy controls, the aggregate serum protein profile in the WSiMD cohort was dominated by muscle proteins, reflecting leak of muscle proteins into serum. Disease status produced more proteins differentially present in serum compared to steroid-treatment effect. Nonetheless, a response to prednisone was discernable in the WSiMD cohort, even at this low dose. Glucocorticoids downregulated muscle proteins and upregulated certain immune process- and matrix-associated proteins. Muscle MR fat fraction showed trends with functional status. The prednisone-responsive markers could be used in larger trial of prednisone efficacy.

RhoA Is a Crucial Regulator of Myoblast Fusion

Satellite cells (SCs) are adult muscle stem cells that are mobilized when muscle homeostasis is perturbed. Here we show that RhoA in SCs is indispensable to have correct muscle regeneration and hypertrophy. In particular, the absence of RhoA in SCs prevents a correct SC fusion both to other RhoA-deleted SCs (regeneration context) and to growing control myofibers (hypertrophy context). We demonstrated that RhoA is dispensable for SCs proliferation and differentiation; however, RhoA-deleted SCs have an inefficient movement even if their cytoskeleton assembly is not altered. Proliferative myoblast and differentiated myotubes without RhoA display a decreased expression of Chordin, suggesting a crosstalk between these genes for myoblast fusion regulation. These findings demonstrate the importance of RhoA in SC fusion regulation and its requirement to achieve an efficient skeletal muscle homeostasis restoration.

Intranasal insulin treatment partially corrects the altered gene expression profile in the hippocampus of developing rats with perinatal iron deficiency

Perinatal iron deficiency (FeD) targets the hippocampus and leads to long-term cognitive deficits. Intranasal insulin administration improves cognitive deficits in adult humans with Alzheimer's disease and type 2 diabetes and could provide benefits in FeD-induced hippocampal dysfunction. To objective was to assess the effects of intranasal insulin administration intranasal insulin administration on the hippocampal transcriptome in a developing rat model of perinatal FeD. Perinatal FeD was induced using low-iron diet from gestational day 3 until postnatal day (P) 7, followed by an iron sufficient (FeS) diet through P21. Intranasal insulin was administered at a dose of 0.3 IU twice daily from P8 to P21. Hippocampi were removed on P21 from FeS control, FeD control, FeS insulin, and FeD insulin groups. Total RNA was isolated and profiled using next-generation sequencing. Gene expression profiles were characterized using custom workflows and expression patterns examined using ingenuity pathways analysis (n = 7-9 per group). Select RNAseq results were confirmed via qPCR. Transcriptomic profiling revealed that mitochondrial biogenesis and flux, oxidative phosphorylation, quantity of neurons, CREB signaling in neurons, and RICTOR-based mTOR signaling were disrupted with FeD and positively affected by intranasal insulin treatment with the most benefit observed in the FeD insulin group. Both perinatal FeD and intranasal insulin administration altered gene expression profile in the developing hippocampus. Intranasal insulin treatment reversed the adverse effects of FeD on many molecular pathways and could be explored as an adjunct therapy in perinatal FeD.

The Rho GTPase exchange factor Vav2 promotes extensive age-dependent rewiring of the hair follicle stem cell transcriptome

Both the number and regenerative activity of hair follicle stem cells (HFSCs) are regulated by Vav2, a GDP/GTP exchange factor involved in the catalytic stimulation of the GTPases Rac1 and RhoA. However, whether Vav2 signaling changes in HFSCs over the mouse lifespan is not yet known. Using a mouse knock-in mouse model, we now show that the expression of a catalytically active version of Vav2 (Vav2Onc) promotes an extensive rewiring of the overall transcriptome of HFSCs, the generation of new transcription factor hubs, and the synchronization of many transcriptional programs associated with specific HFSC states and well-defined signaling pathways. Interestingly, this transcriptome rewiring is not fixed in time, as it involves the induction of 15 gene expression waves with diverse distribution patterns during the life of the animals. These expression waves are consistent with the promotion by Vav2Onc of several functional HFSC states that differ from those normally observed in wild-type HFSCs. These results further underscore the role of Vav2 in the regulation of the functional state of HFSCs. They also indicate that, unlike other Vav2-dependent biological processes, the signaling output of this exchange factor is highly contingent on age-dependent intrinsic and/or extrinsic HFSC factors that shape the final biological readouts triggered in this cell type.

PI3K signaling-regulated metabolic reprogramming: From mechanism to application

Oncogenic signaling involved in tumor metabolic reprogramming. Tumorigenesis was not only determined by the mutations or deletion of oncogenes but also accompanied by the reprogramming of cellular metabolism. Metabolic alterations play a crucial regulatory role in the development and progression of tumors. Oncogenic PI3K/AKT signaling mediates the metabolic switch in cancer cells and immune cells in the tumor microenvironment. PI3K/AKT and its downstream effector branch off and connect to multiple steps of metabolism, such as glucose, lipids, and amino acids. Thus, PI3K inhibitor could effectively regulate metabolic pathway and impede the oncogenic process and some key metabolic proteins or critical enzymes also constitute biomarkers for tumor diagnosis and treatment. In the current review, we summarize the significant effect of PI3K/AKT signaling toward tumor metabolism, it enables us to obtain the better understanding for this interaction and develop more effective therapeutic strategies targeting cancer cell metabolism.

The transcription regulator ATF4 is a mediator of skeletal muscle aging

Aging slowly erodes skeletal muscle strength and mass, eventually leading to profound functional deficits and muscle atrophy. The molecular mechanisms of skeletal muscle aging are not well understood. To better understand mechanisms of muscle aging, we investigated the potential role of ATF4, a transcription regulatory protein that can rapidly promote skeletal muscle atrophy in young animals deprived of adequate nutrition or activity. To test the hypothesis that ATF4 may be involved in skeletal muscle aging, we studied fed and active muscle-specific ATF4 knockout mice (ATF4 mKO mice) at 6 months of age, when wild-type mice have achieved peak muscle mass and function, and at 22 months of age, when wild-type mice have begun to manifest age-related muscle atrophy and weakness. We found that 6-month-old ATF4 mKO mice develop normally and are phenotypically indistinguishable from 6-month-old littermate control mice. However, as ATF4 mKO mice become older, they exhibit significant protection from age-related declines in strength, muscle quality, exercise capacity, and muscle mass. Furthermore, ATF4 mKO muscles are protected from some of the transcriptional changes characteristic of normal muscle aging (repression of certain anabolic mRNAs and induction of certain senescence-associated mRNAs), and ATF4 mKO muscles exhibit altered turnover of several proteins with important roles in skeletal muscle structure and metabolism. Collectively, these data suggest ATF4 as an essential mediator of skeletal muscle aging and provide new insight into a degenerative process that impairs the health and quality of life of many older adults.

The Rho guanine dissociation inhibitor α inhibits skeletal muscle Rac1 activity and insulin action

The molecular events governing skeletal muscle glucose uptake have pharmacological potential for managing insulin resistance in conditions such as obesity, diabetes, and cancer. With no current pharmacological treatments to target skeletal muscle insulin sensitivity, there is an unmet need to identify the molecular mechanisms that control insulin sensitivity in skeletal muscle. Here, the Rho guanine dissociation inhibitor α (RhoGDIα) is identified as a point of control in the regulation of insulin sensitivity. In skeletal muscle cells, RhoGDIα interacted with, and thereby inhibited, the Rho GTPase Rac1. In response to insulin, RhoGDIα was phosphorylated at S101 and Rac1 dissociated from RhoGDIα to facilitate skeletal muscle GLUT4 translocation. Accordingly, siRNA-mediated RhoGDIα depletion increased Rac1 activity and elevated GLUT4 translocation. Consistent with RhoGDIα's inhibitory effect, rAAV-mediated RhoGDIα overexpression in mouse muscle decreased insulin-stimulated glucose uptake and was detrimental to whole-body glucose tolerance. Aligning with RhoGDIα's negative role in insulin sensitivity, RhoGDIα protein content was elevated in skeletal muscle from insulin-resistant patients with type 2 diabetes. These data identify RhoGDIα as a clinically relevant controller of skeletal muscle insulin sensitivity and whole-body glucose homeostasis, mechanistically by modulating Rac1 activity.

Integration of non-additive genome-wide association study with a multi-tissue transcriptome analysis of growth and carcass traits in Duroc pigs

Growth and carcass traits are of economic importance in the pig production, which affect pork quality and profitability of finishing pig production. This study used whole-genome and transcriptome sequencing technologies to identify potential candidate genes affecting growth and carcass traits in Duroc pigs. The medium (50-60 k) single nucleotide polymorphism (SNP) arrays of 4 154 Duroc pigs from three populations were imputed to whole-genome sequence data, yielding 10 463 227 markers on 18 autosomes. The dominance heritabilities estimated for growth and carcass traits ranged from 0.000 ± 0.041 to 0.161 ± 0.054. Using non-additive genome-wide association study (GWAS), we identified 80 dominance quantitative trait loci for growth and carcass traits at genome-wide significance (false discovery rate < 5%), 15 of which were also detected in our additive GWAS. After fine mapping, 31 candidate genes for dominance GWAS were annotated, and 8 of them were highlighted that have been previously reported to be associated with growth and development (e.g. SNX14, RELN and ENPP2), autosomal recessive diseases (e.g. AMPH, SNX14, RELN and CACNB4) and immune response (e.g. UNC93B1 and PPM1D). By integrating the lead SNPs with RNA-seq data of 34 pig tissues from the Pig Genotype-Tissue Expression project (https://piggtex.farmgtex.org/), we found that the rs691128548, rs333063869, and rs1110730611 have significantly dominant effects for the expression of SNX14, AMPH and UNC93B1 genes in tissues related to growth and development for pig, respectively. Finally, the identified candidate genes were significantly enriched for biological processes involved in the cell and organ development, lipids catabolic process and phosphatidylinositol 3-kinase signalling (P < 0.05). These results provide new molecular markers for meat production and quality selection of pig as well as basis for deciphering the genetic mechanisms of growth and carcass traits.

Silencing of RhoC induces macrophage M1 polarization to inhibit migration and invasion in colon cancer via regulating the PTEN/FOXO1 pathway

Ras homologue family member C (RhoC) is an oncogene in diverse types of human cancers, whereas its regulatory mechanisms involving macrophage polarization is rarely investigated. This study is designed to explore the regulatory role of RhoC in colon cancer and the underlying molecular mechanisms involving macrophage polarization. We detected RhoC expression by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot, and analysed the biological function of RhoC knockdown in CC cells by the MTT, wound healing and transwell assay. Macrophage polarization-associated markers, genes associated with migration, phosphatase and tensin homologue (PTEN) and forkhead box O (FOXO) were determined by qRT-PCR and western blot. The xenograft tumour mouse model was used to assess the role of RhoC in vivo. RhoC is highly expressed in CC cells. The cell viability, invasion and migration abilities of CC cells were reduced by knockdown of RhoC. RhoC knockdown promoted M1 polarization, inhibited M2 polarization and decreased levels of genes associated with migration (matrix metalloproteinase-2 and matrix metalloproteinase-9). Silencing of RhoC inhibited tumour growth and expression of genes associated with migration in the xenografted model. In addition, silencing of RhoC promoted PTEN/FOXO1 expression, and PTEN inhibitor (SF1670) reversed the inhibitory effects of RhoC silencing. We demonstrated that silencing of RhoC reduced CC cells invasion and migration, and tumour growth by suppressing M2 macrophage polarization via regulating the PTEN/FOXO1 pathway.

Vav2 is a novel APP-interacting protein that regulates APP protein level

Amyloid precursor protein (APP) is a transmembrane protein that plays critical role in the pathogenesis of Alzheimer's disease (AD). It is also involved in many types of cancers. Increasing evidence has shown that the tyrosine phosphorylation site Y682 in the intracellular tail of APP is crucial for APP function. Here, we report that Vav2, a guanine nucleotide exchange factor (GEF) for Rho family GTPase, is a novel interaction partner of APP. We found that Vav2-SH2 domain was able to bind directly to the Y682-phosphorylated intracellular tail of APP through isothermal titration calorimetry and NMR titrating experiments. The crystal structure of Vav2-SH2 in complex with an APP-derived phosphopeptide was determined to understand the structural basis of this recognition specificity. The interaction of APP and Vav2 in a full-length manner was further confirmed in cells by GST pull-down, co-immunoprecipitation and immunofluorescence staining experiments. In addition, we found overexpression of Vav2 could inhibit APP degradation and markedly increase the protein levels of APP and its cleavage productions in 20E2 cells, and this function of Vav2 required a functional SH2 domain.

The Rho guanosine nucleotide exchange factors Vav2 and Vav3 modulate epidermal stem cell function

It is known that Rho GTPases control different aspects of the biology of skin stem cells (SSCs). However, little information is available on the role of their upstream regulators under normal and tumorigenic conditions in this process. To address this issue, we have used here mouse models in which the activity of guanosine nucleotide exchange factors of the Vav subfamily has been manipulated using both gain- and loss-of-function strategies. These experiments indicate that Vav2 and Vav3 regulate the number, functional status, and responsiveness of hair follicle bulge stem cells. This is linked to gene expression programs related to the reinforcement of the identity and the quiescent state of normal SSCs. By contrast, in the case of cancer stem cells, they promote transcriptomal programs associated with the identity, activation state, and cytoskeletal remodeling. These results underscore the role of these Rho exchange factors in the regulation of normal and tumor epidermal stem cells.

Insight Into Rho Kinase Isoforms in Obesity and Energy Homeostasis

Obesity and associated complications increasingly jeopardize global health and contribute to the rapidly rising prevalence of type 2 diabetes mellitus and obesity-related diseases. Developing novel methods for the prevention and treatment of excess body adipose tissue expansion can make a significant contribution to public health. Rho kinase is a Rho-associated coiled-coil-containing protein kinase (Rho kinase or ROCK). The ROCK family including ROCK1 and ROCK2 has recently emerged as a potential therapeutic target for the treatment of metabolic disorders. Up-regulated ROCK activity has been involved in the pathogenesis of all aspects of metabolic syndrome including obesity, insulin resistance, dyslipidemia and hypertension. The RhoA/ROCK-mediated actin cytoskeleton dynamics have been implicated in both white and beige adipogenesis. Studies using ROCK pan-inhibitors in animal models of obesity, diabetes, and associated complications have demonstrated beneficial outcomes. Studies via genetically modified animal models further established isoform-specific roles of ROCK in the pathogenesis of metabolic disorders including obesity. However, most reported studies have been focused on ROCK1 activity during the past decade. Due to the progress in developing ROCK2-selective inhibitors in recent years, a growing body of evidence indicates more attention should be devoted towards understanding ROCK2 isoform function in metabolism. Hence, studying individual ROCK isoforms to reveal their specific roles and principal mechanisms in white and beige adipogenesis, insulin sensitivity, energy balancing regulation, and obesity development will facilitate significant breakthroughs for systemic treatment with isoform-selective inhibitors. In this review, we give an overview of ROCK functions in the pathogenesis of obesity and insulin resistance with a particular focus on the current understanding of ROCK isoform signaling in white and beige adipogenesis, obesity and thermogenesis in adipose tissue and other major metabolic organs involved in energy homeostasis regulation.

Bioprocessing technology of muscle stem cells: implications for cultured meat

Muscle stem cells (MuSCs) are essential for the growth, maintenance, and repair of skeletal muscle. In the emerging area of cultured meat, meat products are manufactured with MuSCs using theory and technology from the fields of cell culture, tissue engineering, and food processing. Recently, considerable progress has been made in bioprocessing technologies for MuSCs, including isolation, expansion, differentiation, and tissue building. Here we summarize cutting-edge operational strategies and recently characterized regulatory mechanisms for MuSCs. Furthermore, we discuss their applicability to refining the production process for cultured meat and accelerating its industrialization.

Rho GTPases in Skeletal Muscle Development and Homeostasis

Rho guanosine triphosphate hydrolases (GTPases) are molecular switches that cycle between an inactive guanosine diphosphate (GDP)-bound and an active guanosine triphosphate (GTP)-bound state during signal transduction. As such, they regulate a wide range of both cellular and physiological processes. In this review, we will summarize recent work on the role of Rho GTPase-regulated pathways in skeletal muscle development, regeneration, tissue mass homeostatic balance, and metabolism. In addition, we will present current evidence that links the dysregulation of these GTPases with diseases caused by skeletal muscle dysfunction. Overall, this information underscores the critical role of a number of members of the Rho GTPase subfamily in muscle development and the overall metabolic balance of mammalian species.

New Functions of Vav Family Proteins in Cardiovascular Biology, Skeletal Muscle, and the Nervous System

Simple Summary

In this review, we provide information on the role of Vav proteins, a group of signaling molecules that act as both Rho GTPase activators and adaptor molecules, in the cardiovascular system, skeletal muscle, and the nervous system. We also describe how these functions impact in other physiological and pathological processes such as sympathoregulation, blood pressure regulation, systemic metabolism, and metabolic syndrome.

Abstract

Vav proteins act as tyrosine phosphorylation-regulated guanosine nucleotide exchange factors for Rho GTPases and as molecular scaffolds. In mammals, this family of signaling proteins is composed of three members (Vav1, Vav2, Vav3) that work downstream of protein tyrosine kinases in a wide variety of cellular processes. Recent work with genetically modified mouse models has revealed that these proteins play key signaling roles in vascular smooth and skeletal muscle cells, specific neuronal subtypes, and glia cells. These functions, in turn, ensure the proper regulation of blood pressure levels, skeletal muscle mass, axonal wiring, and fiber myelination events as well as systemic metabolic balance. The study of these mice has also led to the discovery of new physiological interconnection among tissues that contribute to the ontogeny and progression of different pathologies such as, for example, hypertension, cardiovascular disease, and metabolic syndrome. Here, we provide an integrated view of all these new Vav family-dependent signaling and physiological functions.

The cytoskeleton as a non-cholinergic target of organophosphate compounds

Current organophosphate (OP) toxicity research now considers potential non-cholinergic mechanisms for these compounds, since the inhibition of acetylcholinesterase (AChE) cannot completely explain all the adverse biological effects of OP. Thanks to the development of new strategies for OP detection, some potential molecular targets have been identified. Among these molecules are several cytoskeletal proteins, including actin, tubulin, intermediate filament proteins, and associated proteins, such as motor proteins, microtubule-associated proteins (MAPs), and cofilin. in vitro, ex vivo, and some in vivo reports have identified alterations in the cytoskeleton following OP exposure, including cell morphology defects, cells detachments, intracellular transport disruption, aberrant mitotic spindle formation, modification of cell motility, and reduced phagocytic capability, which implicate the cytoskeleton in OP toxicity. Here, we reviewed the evidence indicating the cytoskeletal targets of OP compounds, including their strategies, the potential effects of their alterations, and their possible participation in neurotoxicity, embryonic development, cell division, and immunotoxicity related to OP compounds exposure.

Rho Family GTPases and Rho GEFs in Glucose Homeostasis

Dysregulation of glucose homeostasis leading to metabolic syndrome and type 2 diabetes is the cause of an increasing world health crisis. New intriguing roles have emerged for Rho family GTPases and their Rho guanine nucleotide exchange factor (GEF) activators in the regulation of glucose homeostasis. This review summates the current knowledge, focusing in particular on the roles of Rho GEFs in the processes of glucose-stimulated insulin secretion by pancreatic β cells and insulin-stimulated glucose uptake into skeletal muscle and adipose tissues. We discuss the ten Rho GEFs that are known so far to regulate glucose homeostasis, nine of which are in mammals, and one is in yeast. Among the mammalian Rho GEFs, P-Rex1, Vav2, Vav3, Tiam1, Kalirin and Plekhg4 were shown to mediate the insulin-stimulated translocation of the glucose transporter GLUT4 to the plasma membrane and/or insulin-stimulated glucose uptake in skeletal muscle or adipose tissue. The Rho GEFs P-Rex1, Vav2, Tiam1 and β-PIX were found to control the glucose-stimulated release of insulin by pancreatic β cells. In vivo studies demonstrated the involvement of the Rho GEFs P-Rex2, Vav2, Vav3 and PDZ-RhoGEF in glucose tolerance and/or insulin sensitivity, with deletion of these GEFs either contributing to the development of metabolic syndrome or protecting from it. This research is in its infancy. Considering that over 80 Rho GEFs exist, it is likely that future research will identify more roles for Rho GEFs in glucose homeostasis.