Role of Rho-kinase in regulation of insulin action and glucose homeostasis

Effects of a protein kinase C epsilon inhibitor on insulin signalling in lipid-treated HepG2 hepatocytes and glucose tolerance in fat-fed mice

AIMS

Protein kinase C epsilon (PKCε) plays a causative role in the development of glucose intolerance, and is a potential target for the treatment of type 2 diabetes. Here, we examined the effects of the PKCε inhibitor CIDD-0150612 (CP612) on insulin action in palmitate-treated HepG2 hepatocytes in vitro and on glucose homeostasis in fat-fed mice in vivo.

METHODS

HepG2 cells were treated with palmitate and CP612 and stimulated with insulin. Insulin signalling was examined by immunoblotting and glucose incorporation into glycogen was measured using glucose tracer. Mice were fed a high-fat diet and treated with CP612 prior to glucose tolerance tests and tissue harvest. Proteomic analysis of liver was carried out by mass spectrometry.

RESULTS

CP612 promoted Akt phosphorylation in a highly insulin-dependent manner and reversed the inhibition of insulin-stimulated Akt phosphorylation and glucose incorporation into glycogen by palmitate. Fat-fed mice treated with CP612 had reduced fat mass, but not lean mass, compared with vehicle-treated littermates. Mice treated acutely with CP612 exhibited elevated fasting blood glucose. However, mice studied 24h after the last dose had lower fasting glucose and improved glucose tolerance with a lower insulin excursion. Proteomic analysis of liver from CP612-treated fat-fed mice indicated a reduction in gluconeogenic gene expression and decreased phosphorylation of the transcription factor Foxk1.

CONCLUSIONS

The PKCε inhibitor CP612 had beneficial effects on insulin action in hepatocytes and on fat mass and glucose homeostasis in mice. Because certain effects were not previously observed in genetically PKCε-deficient mice, off-target effects may be partly responsible.

Mechanical Stretch Control of Adipocyte AKT Signaling and the Role of FAK and ROCK Mechanosensors

Adipose tissue in vivo is physiologically exposed to compound mechanical loading due to bodyweight bearing, posture, and motion. The capability of adipocytes to sense and respond to mechanical loading milieus to influence metabolic functions may provide a new insight into obesity and metabolic diseases such as type 2 diabetes (T2D). Here, we evidenced physiological mechanical loading control of adipocyte insulin signaling cascades. We exposed differentiated 3T3-L1 adipocytes to mechanical stretching and assessed key markers of insulin signaling, AKT activation, and GLUT4 translocation, required for glucose uptake. We showed that cyclic stretch loading at 5% strain and 1 Hz frequency increases AKT phosphorylation and GLUT4 translocation to the plasma membrane by approximately two-fold increases compared to unstretched controls for both markers as assessed by immunoblotting (p < 0.05). These results indicate that cyclic stretching activates insulin signaling and GLUT4 trafficking in adipocytes. In the mechanosensing mechanism study, focal adhesion kinase (FAK) inhibitor (FAK14) and RhoA kinase (ROCK) inhibitor (Y-27632) impaired actin cytoskeleton structural formation and significantly suppressed the stretch induction of AKT phosphorylation in adipocytes (p < 0.001). This suggests the regulatory role of focal adhesion and cytoskeletal mechanosensing in adipocyte insulin signaling under stretch loading. Our finding on the impact of mechanical stretch loading on key insulin signaling effectors in differentiated adipocytes and the mediatory role of focal adhesion and cytoskeleton mechanosensors is the first of its kind to our knowledge. This may suggest a therapeutic potential of mechanical loading cue in improving conditions of obesity and T2D. For instance, cyclic mechanical stretch loading of adipose tissue could be explored as a tool to improve insulin sensitivity in patients with obesity and T2D, and the mediatory mechanosensors such as FAK and ROCK may be targeted to further invigorate stretch-induced insulin signaling activation.

Therapeutic modulation of ROCK overcomes metabolic adaptation of cancer cells to OXPHOS inhibition and drives synergistic anti-tumor activity

Genomic studies have identified frequent mutations in subunits of the SWI/SNF chromatin remodeling complex including SMARCA4 and ARID1A in non-small cell lung cancer. Previously, we and others have identified that SMARCA4-mutant lung cancers are highly dependent on oxidative phosphorylation (OXPHOS). Despite initial excitements, therapeutics targeting metabolic pathways such as OXPHOS have largely been disappointing due to rapid adaptation of cancer cells to inhibition of single metabolic enzymes or pathways, suggesting novel combination strategies to overcome adaptive responses are urgently needed. Here, we performed a functional genomics screen using CRISPR-Cas9 library targeting genes with available FDA approved therapeutics and identified ROCK1/2 as a top hit that sensitizes cancer cells to OXPHOS inhibition. We validate these results by orthogonal genetic and pharmacologic approaches by demonstrating that KD025 (Belumosudil), an FDA approved ROCK inhibitor, has highly synergistic anti-cancer activity in vitro and in vivo in combination with OXPHOS inhibition. Mechanistically, we showed that this combination induced a rapid, profound energetic stress and cell cycle arrest that was in part due to ROCK inhibition-mediated suppression of the adaptive increase in glycolysis normally seen by OXPHOS inhibition. Furthermore, we applied global phosphoproteomics and kinase-motif enrichment analysis to uncover a dynamic regulatory kinome upon combination of OXPHOS and ROCK inhibition. Importantly, we found converging phosphorylation-dependent regulatory cross-talk by AMPK and ROCK kinases on key RHO GTPase signaling/ROCK-dependent substrates such as PPP1R12A, NUMA1 and PKMYT1 that are known regulators of cell cycle progression. Taken together, our study identified ROCK kinases as critical mediators of metabolic adaptation of cancer cells to OXPHOS inhibition and provides a strong rationale for pursuing ROCK inhibitors as novel combination partners to OXPHOS inhibitors in cancer treatment.

Unraveling the rationale and conducting a comprehensive assessment of KD025 (Belumosudil) as a candidate drug for inhibiting adipogenic differentiation-a systematic review

Rho-associated kinases (ROCKs) are crucial during the adipocyte differentiation process. KD025 (Belumosudil) is a newly developed inhibitor that selectively targets ROCK2. It has exhibited consistent efficacy in impeding adipogenesis across a spectrum of in vitro models of adipogenic differentiation. Given the novelty of this treatment, a comprehensive systematic review has not been conducted yet. This systematic review aims to fill this knowledge void by providing readers with an extensive examination of the rationale behind KD025 and its impacts on adipogenesis. Preclinical evidence was gathered owing to the absence of clinical trials. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, and the study's quality was assessed using the Joanna Briggs Institute (JBI) Checklist Critical Appraisal Tool for Systematic Reviews. In various in vitro models, such as 3T3-L1 cells, human orbital fibroblasts, and human adipose-derived stem cells, KD025 demonstrated potent anti-adipogenic actions. At a molecular level, KD025 had significant effects, including decreasing fibronectin (Fn) expression, inhibiting ROCK2 and CK2 activity, suppressing lipid droplet formation, and reducing the expression of proadipogenic genes peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα). Additionally, KD025 resulted in the suppression of fatty acid-binding protein 4 (FABP4 or AP2) expression, a decrease in sterol regulatory element binding protein 1c (SREBP-1c) and Glut-4 expression. Emphasis must be placed on the fact that while KD025 shows potential in preclinical studies and experimental models, extensive research is crucial to assess its efficacy, safety, and potential therapeutic applications thoroughly and directly in human subjects.

RhoA activation promotes glucose uptake to elevate proliferation in MAPK inhibitor resistant melanoma cells

Cutaneous melanomas harboring a B-RafV600E mutation are treated with immune check point inhibitors or kinase inhibitor combination therapies relying on MAPK inhibitors (MAPKi) Dabrafenib and Trametinib (Curti and Faries, 2021). However, cells become resistant to treatments over the timespan of a few months. Resistance to MAPKi has been associated with adoption of an aggressive amoeboid phenotype characterized by elevated RhoA signaling, enhanced contractility and thick cortical filamentous actin (F-actin) structures (Kim et al., 2016; Misek et al., 2020). Targeting active RhoA through Rho-kinase (ROCK) inhibitors, either alone or in combination with immunotherapies, reverts MAPKi-resistance (Misek et al., 2020; Orgaz et al., 2020). Yet, the mechanisms for this behavior remain largely unknown. Given our recent findings of cytoskeleton's role in cancer cell proliferation (Mohan et al., 2019), survival (Weems et al., 2023), and metabolism (Park et al., 2020), we explored possibilities by which RhoA-driven changes in cytoskeleton structure may confer resistance. We confirmed elevated activation of RhoA in a panel of MAPKi-resistant melanoma cell lines, leading to a marked increase in the presence of contractile F-actin bundles. Moreover, these cells had increased glucose uptake and glycolysis, a phenotype disrupted by pharmacological perturbation of ROCK. However, glycolysis was unaffected by disruption of F-actin bundles, indicating that glycolytic stimulation in MAPKi-resistant melanoma is independent of F-actin organization. Instead, our findings highlight a mechanism in which elevated RhoA signaling activates ROCK, leading to the activation of insulin receptor substrate 1 (IRS1) and P85 of the PI3K pathway, which promotes cell surface expression of GLUT1 and elevated glucose uptake. Application of ROCK inhibitor GSK269962A results in reduced glucose uptake and glycolysis, thus impeding cell proliferation. Our study adds a mechanism to the proposed use of ROCK inhibitors for long-term treatments on MAPKi-resistant melanomas.

Combining bioinformatics and machine learning algorithms to identify and analyze shared biomarkers and pathways in COVID-19 convalescence and diabetes mellitus

Background

Most patients who had coronavirus disease 2019 (COVID-19) fully recovered, but many others experienced acute sequelae or persistent symptoms. It is possible that acute COVID-19 recovery is just the beginning of a chronic condition. Even after COVID-19 recovery, it may lead to the exacerbation of hyperglycemia process or a new onset of diabetes mellitus (DM). In this study, we used a combination of bioinformatics and machine learning algorithms to investigate shared pathways and biomarkers in DM and COVID-19 convalescence.

Methods

Gene transcriptome datasets of COVID-19 convalescence and diabetes mellitus from Gene Expression Omnibus (GEO) were integrated using bioinformatics methods and differentially expressed genes (DEGs) were found using the R programme. These genes were also subjected to Gene Ontology (GO) functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis to find potential pathways. The hub DEGs genes were then identified by combining protein-protein interaction (PPI) networks and machine learning algorithms. And transcription factors (TFs) and miRNAs were predicted for DM after COVID-19 convalescence. In addition, the inflammatory and immune status of diabetes after COVID-19 convalescence was assessed by single-sample gene set enrichment analysis (ssGSEA).

Results

In this study, we developed genetic diagnostic models for 6 core DEGs beteen type 1 DM (T1DM) and COVID-19 convalescence and 2 core DEGs between type 2 DM (T2DM) and COVID-19 convalescence and demonstrated statistically significant differences (p<0.05) and diagnostic validity in the validation set. Analysis of immune cell infiltration suggests that a variety of immune cells may be involved in the development of DM after COVID-19 convalescence.

Conclusion

We identified a genetic diagnostic model for COVID-19 convalescence and DM containing 8 core DEGs and constructed a nomogram for the diagnosis of COVID-19 convalescence DM.

Local glycolysis fuels actomyosin contraction during axonal retraction

In response to repulsive cues, axonal growth cones can quickly retract. This requires the prompt activity of contractile actomyosin, which is formed by the non-muscle myosin II (NMII) bound to actin filaments. NMII is a molecular motor that provides the necessary mechanical force at the expense of ATP. Here, we report that this process is energetically coupled to glycolysis and is independent of cellular ATP levels. Induction of axonal retraction requires simultaneous generation of ATP by glycolysis, as shown by chemical inhibition and genetic knock-down of GAPDH. Co-immunoprecipitation and proximal-ligation assay showed that actomyosin associates with ATP-generating glycolytic enzymes and that this association is strongly enhanced during retraction. Using microfluidics, we confirmed that the energetic coupling between glycolysis and actomyosin necessary for axonal retraction is localized to the growth cone and near axonal shaft. These results indicate a tight coupling between on-demand energy production by glycolysis and energy consumption by actomyosin contraction suggesting a function of glycolysis in axonal guidance.

Development and validation of a multivariable genotype-informed gestational diabetes prediction algorithm for clinical use in the Mexican population: insights into susceptibility mechanisms

INTRODUCTION

Gestational diabetes mellitus (GDM) is underdiagnosed in Mexico. Early GDM risk stratification through prediction modeling is expected to improve preventative care. We developed a GDM risk assessment model that integrates both genetic and clinical variables.

RESEARCH DESIGN AND METHODS

Data from pregnant Mexican women enrolled in the 'Cuido mi Embarazo' (CME) cohort were used for development (107 cases, 469 controls) and data from the 'Mónica Pretelini Sáenz' Maternal Perinatal Hospital (HMPMPS) cohort were used for external validation (32 cases, 199 controls). A 2-hour oral glucose tolerance test (OGTT) with 75 g glucose performed at 24-28 gestational weeks was used to diagnose GDM. A total of 114 single-nucleotide polymorphisms (SNPs) with reported predictive power were selected for evaluation. Blood samples collected during the OGTT were used for SNP analysis. The CME cohort was randomly divided into training (70% of the cohort) and testing datasets (30% of the cohort). The training dataset was divided into 10 groups, 9 to build the predictive model and 1 for validation. The model was further validated using the testing dataset and the HMPMPS cohort.

RESULTS

Nineteen attributes (14 SNPs and 5 clinical variables) were significantly associated with the outcome; 11 SNPs and 4 clinical variables were included in the GDM prediction regression model and applied to the training dataset. The algorithm was highly predictive, with an area under the curve (AUC) of 0.7507, 79% sensitivity, and 71% specificity and adequately powered to discriminate between cases and controls. On further validation, the training dataset and HMPMPS cohort had AUCs of 0.8256 and 0.8001, respectively.

CONCLUSIONS

We developed a predictive model using both genetic and clinical factors to identify Mexican women at risk of developing GDM. These findings may contribute to a greater understanding of metabolic functions that underlie elevated GDM risk and support personalized patient recommendations.

Glycosphingolipids in Diabetes, Oxidative Stress, and Cardiovascular Disease: Prevention in Experimental Animal Models

Diabetes contributes to about 30% morbidity and mortality world-wide and has tidal wave increases in several countries in Asia. Diabetes is a multi-factorial disease compounded by inflammation, dyslipidemia, atherosclerosis, and is sometimes accompanied with gains in body weight. Sphingolipid pathways that interplay in the enhancement of the pathology of this disease may be potential therapeutic targets. Thus, the application of advanced sphingolipidomics may help predict the progression of this disease and therapeutic outcomes in man. Pre-clinical studies using various experimental animal models of diabetes provide valuable information on the role of sphingolipid signaling networks in diabetes and the efficacy of drugs to determine the translatability of innovative discoveries to man. In this review, we discuss three major concepts regarding sphingolipids and diabetes. First, we discuss a possible involvement of a monosialodihexosylceramide (GM3) in insulin-insulin receptor interactions. Second, a potential role for ceramide (Cer) and lactosylceramide (LacCer) in apoptosis and mitochondrial dysfunction is proposed. Third, a larger role of LacCer in antioxidant status and inflammation is discussed. We also discuss how inhibitors of glycosphingolipid synthesis can ameliorate diabetes in experimental animal models.

ROCK1 regulates insulin secretion from β-cells

OBJECTIVE

The endocrine pancreatic β-cells play a pivotal role in maintaining whole-body glucose homeostasis and its dysregulation is a consistent feature in all forms of diabetes. However, knowledge of intracellular regulators that modulate β-cell function remains incomplete. We investigated the physiological role of ROCK1 in the regulation of insulin secretion and glucose homeostasis.

METHODS

Mice lacking ROCK1 in pancreatic β-cells (RIP-Cre; ROCK1loxP/loxP, β-ROCK1-/-) were studied. Glucose and insulin tolerance tests as well as glucose-stimulated insulin secretion (GSIS) were measured. An insulin secretion response to a direct glucose or pyruvate or pyruvate kinase (PK) activator stimulation in isolated islets from β-ROCK1-/- mice or β-cell lines with knockdown of ROCK1 was also evaluated. A proximity ligation assay was performed to determine the physical interactions between PK and ROCK1.

RESULTS

Mice with a deficiency of ROCK1 in pancreatic β-cells exhibited significantly increased blood glucose levels and reduced serum insulin without changes in body weight. Interestingly, β-ROCK1-/- mice displayed a progressive impairment of glucose tolerance while maintaining insulin sensitivity mostly due to impaired GSIS. Consistently, GSIS markedly decreased in ROCK1-deficient islets and ROCK1 knockdown INS-1 cells. Concurrently, ROCK1 blockade led to a significant decrease in intracellular calcium and ATP levels and oxygen consumption rates in isolated islets and INS-1 cells. Treatment of ROCK1-deficient islets or ROCK1 knockdown β-cells either with pyruvate or a PK activator rescued the impaired GSIS. Mechanistically, we observed that glucose stimulation in β-cells greatly enhanced ROCK1 binding to PK.

CONCLUSIONS

Our findings demonstrate that β-cell ROCK1 is essential for glucose-stimulated insulin secretion and for glucose homeostasis and that ROCK1 acts as an upstream regulator of glycolytic pyruvate kinase signaling.

Reduced Tyrosine and Serine-632 Phosphorylation of Insulin Receptor Substrate-1 in the Gastrocnemius Muscle of Obese Zucker Rat

Obesity has become a serious health problem in the world, with increased morbidity, mortality, and financial burden on patients and health-care providers. The skeletal muscle is the most extensive tissue, severely affected by a sedentary lifestyle, which leads to obesity and type 2 diabetes. Obesity disrupts insulin signaling in the skeletal muscle, resulting in decreased glucose disposal, a condition known as insulin resistance. Although there is a large body of evidence on obesity-induced insulin resistance in various skeletal muscles, the molecular mechanism of insulin resistance due to a disruption in insulin receptor signaling, specifically in the gastrocnemius skeletal muscle of obese Zucker rats (OZRs), is not fully understood. This study subjected OZRs to a glucose tolerance test (GTT) to analyze insulin sensitivity. In addition, immunoprecipitation and immunoblotting techniques were used to determine the expression and tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and insulin receptor-β (IRβ), and the activation of serine-632-IRS-1 phosphorylation in the gastrocnemius muscle of Zucker rats. The results show that the GTT in the OZRs was impaired. There was a significant decrease in IRS-1 levels, but no change was observed in IRβ in the gastrocnemius muscle of OZRs, compared to Zucker leans. Obese rats had a higher ratio of tyrosine phosphorylation of IRS-1 and IRβ than lean rats. In obese rats, however, insulin was unable to induce tyrosine phosphorylation. Moreover, insulin increased the phosphorylation of serine 632-IRS-1 in the gastrocnemius muscle of lean rats. However, obese rats had a low basal level of serine-632-IRS-1 and insulin only mildly increased serine phosphorylation in obese rats, compared to those without insulin. Thus, we addressed the altered steps of the insulin receptor signal transduction in the gastrocnemius muscle of OZRs. These findings may contribute to a better understanding of human obesity and type 2 diabetes.

Rho-associated kinase1 promotes laryngeal squamous cell carcinoma tumorigenesis and progression via the FAK signaling pathway

Laryngeal squamous cell carcinoma (LSCC) is one of the most common head and neck squamous cell carcinomas (HNSCC). Rho-associated kinase1 (ROCK1) is considered to promote progression of numerous cancers, however, its role in LSCC is still unknown. Here, the expression level of ROCK1 is higher in LSCC tissues than non-tumor tissues, and the expression level of ROCK1 is positively correlated with advanced stage and poor survival prognosis. ROCK1 knockdown in TU686 and TU212 cells dramatically inhibits cellular proliferation, migration and invasion. Whereas the overexpression of ROCK1 reversed these changes. FAK signaling pathway plays an essential role in promoting LSCC progression. Inhibiting FAK activity with TAE226 observably impairs the tumor-promoting effects. In conclusion, ROCK1 promotes LSCC tumorigenesis and progression via the FAK signaling pathway, targeting the ROCK1 molecule may represent potential targets for clinical LSCC treatment.

A bioactive component of Portulaca Oleracea L., HM-chromanone, improves palmitate-induced insulin resistance by inhibiting mTOR/S6K1 through activation of the AMPK pathway in L6 skeletal muscle cells

Increased free fatty acid levels in the blood are common in obesity and cause insulin resistance associated with type 2 diabetes in the muscles. Previous studies have confirmed the antidiabetic and anti-obesity potential of (E)-5-hydroxy-7-methoxy-3-(2-hydroxybenzyl)-4-chromanone (HM-chromanone). However, it is unknown how HM-chromanone alleviates obesity-related insulin resistance in L6 skeletal muscle cells. Palmitate induced insulin resistance and reduced glucose uptake, whereas HM-chromanone significantly increased glucose uptake. In palmitate-treated L6 skeletal muscle cells, HM-chromanone stimulated liver kinase B1 (LKB1) and 5'-adenosine monophosphate-activated protein kinase (AMPK) phosphorylation. The AMPK inhibitor compound C, and the LKB1 inhibitor radicicol blocked the effects of HM-chromanone. Furthermore, HM-chromanone significantly inhibited mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase 1 (S6K1) activation, but there was no change in protein kinase C θ (PKC θ) expression. When pAMPK was inhibited with compound C, the effect of HM-chromanone on the inhibition of mTOR and S6K1 was significantly diminished. This indicates that HM-chromanone inhibits mTOR and S6K1 activation through pAMPK activation. Inhibition of mTOR and S6K1 by HM-chromanone significantly reduced IRS-1Ser307 and IRS-1Ser632 phosphorylation, leading to insulin resistance. This resulted in an increase in PM-GLUT4 (glucose transporter 4) expression, thereby stimulating glucose uptake in insulin-resistant muscle cells. HM-chromanone can improve palmitate-induced insulin resistance by inhibiting mTOR and S6K1 through activation of the AMPK pathway in L6 skeletal muscle cells. These results show the therapeutic potential of HM-chromanone for improving insulin resistance in type 2 diabetes.

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.

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.

Exercise Counterbalances Rho/ROCK2 Signaling Impairment in the Skeletal Muscle and Ameliorates Insulin Sensitivity in Obese Mice

Physical exercise is considered a fundamental strategy in improving insulin sensitivity and glucose uptake in skeletal muscle. However, the molecular mechanisms underlying this regulation, primarily on skeletal muscle glucose uptake, are not fully understood. Recent evidence has shown that Rho-kinase (ROCK) isoforms play a pivotal role in regulating skeletal muscle glucose uptake and systemic glucose homeostasis. The current study evaluated the effect of physical exercise on ROCK2 signaling in skeletal muscle of insulin-resistant obese animals. Physiological (ITT) and molecular analysis (immunoblotting, and RT-qPCR) were performed. The contents of RhoA and ROCK2 protein were decreased in skeletal muscle of obese mice compared to control mice but were restored to normal levels in response to physical exercise. The exercised animals also showed higher phosphorylation of insulin receptor substrate 1 (IRS1 Serine 632/635) and protein kinase B (Akt) in the skeletal muscle. However, phosphatase and tensin homolog (PTEN) and protein-tyrosine phosphatase-1B (PTP-1B), both inhibitory regulators for insulin action, were increased in obesity but decreased after exercise. The impact of ROCK2 action on muscle insulin signaling is further underscored by the fact that impaired IRS1 and Akt phosphorylation caused by palmitate in C2C12 myotubes was entirely restored by ROCK2 overexpression. These results suggest that the exercise-induced upregulation of RhoA-ROCK2 signaling in skeletal muscle is associated with increased systemic insulin sensitivity in obese mice and further implicate that muscle ROCK2 could be a potential target for treating obesity-linked metabolic disorders.

Skeletal Muscle Gene Expression Profile in Response to Caloric Restriction and Aging: A Role for SirT1

SirT1 plays a crucial role in the regulation of some of the caloric restriction (CR) responsive biological pathways. Aging suppresses SirT1 gene expression in skeletal muscle, suggesting that aging may affect the role of CR in muscle. To determine the role of SirT1 in the regulation of CR regulated pathways in skeletal muscle, we performed high-throughput RNA sequencing using total RNA isolated from the skeletal muscles of young and aged wild-type (WT), SirT1 knockout (SirT1-KO), and SirT1 overexpression (SirT1-OE) mice fed to 20 wk ad libitum (AL) or 40% CR diet. Our data show that aging repressed the global gene expression profile, which was restored by CR via upregulating transcriptional and translational process-related pathways. CR inhibits pathways linked to the extracellular matrix and cytoskeletal proteins regardless of aging. Mitochondrial function and muscle contraction-related pathways are upregulated in aged SirT1 KO mice following CR. SirT1 OE did not affect whole-body energy expenditure or augment skeletal muscle insulin sensitivity associated pathways, regardless of aging or diet. Overall, our RNA-seq data showed that SirT1 and CR have different functions and activation of SirT1 by its activator or exercise may enhance SirT1 activity that, along with CR, likely have a better functional role in aging muscle.

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.

[Rho kinase inhibitors as new local therapy option in primary open angle glaucoma]

BACKGROUND

In 2014 in Japan and 2017 in the USA, the Rho-kinase inhibitors were approved as a new antiglaucomatous substance group and will now be launched in Europe.

OBJECTIVE

On this occasion the current state of knowledge on Rho-kinase inhibitors is presented.

METHODS

In intensive search in PubMed the relevant experimental and clinical literature on the Rho-kinase inhibitors ripasudil and netarsudil and the combination of netarsudil and latanoprost were selected and compiled for this review.

RESULTS

The intraocular pressure lowering efficacy of ripasudil and netarsudil is in the range of the beta blocker timolol and the prostaglandin analogue latanoprost. In the fixed combination netarsudil/latanoprost the intraocular pressure reduction is greater than that of the single components and reaches a target pressure of below 15 mm Hg in 32%. Conjunctival hyperemia with 53-65% is the most common local side effect. Systemic side effects are very rare and so far there are no contraindications.

CONCLUSION

The Rho-kinase inhibitors are an interesting new introduction for glaucoma therapy, as each new pressure-lowering therapy represents an additional chance to reach the individually defined target pressure level in a glaucoma patient with local therapy; however, many of the pleiotropic effects associated with Rho-kinase inhibitors have so far only been found experimentally and will require clinical confirmation in the future.

The Effects of Aging on Rho-Kinase and Insulin Signaling in Skeletal Muscle and White Adipose Tissue of Rats

The insulin receptor substrate 1 regulates insulin-mediated glucose uptake and is a target of Rho-kinase (Rock); however, the relationship between age-related insulin resistance and Rock signaling specifically in skeletal muscle and adipose tissue is unknown. We evaluated the content and activity of Rock in C2C12 myotubes, and in skeletal muscle and white adipose tissue (WAT) from two rodent models that differ in their patterns of body fat accumulation during aging (Wistar and Fischer 344 rats). Body fat gain in the Wistar rats was greater than in Fischer rats and only Wistar rats had impairment of whole-body insulin sensitivity. Rock activity and insulin signaling were impaired in skeletal muscle in both rat models, but only middle-aged Wistar rats had higher Rock activity in WAT. These data are consistent with a positive role of Rock in regulating insulin signaling in both skeletal muscle and its negative role in the adipose tissue, suggesting that Rock activity in adipose tissue is important in age-related insulin resistance.

S-Nitrosoglutathione Reverts Dietary Sucrose-Induced Insulin Resistance

The liver is a fundamental organ to ensure whole-body homeostasis, allowing for a proper increase in insulin sensitivity from the fast to the postprandial status. Hepatic regulation of glucose metabolism is crucial and has been shown to be modulated by glutathione (GSH) and nitric oxide (NO). However, knowledge of the metabolic action of GSH and NO in glucose homeostasis remains incomplete. The current study was designed to test the hypothesis that treatment with S-nitrosoglutathione is sufficient to revert insulin resistance induced by a high-sucrose diet. Male Wistar rats were divided in a control or high-sucrose group. Insulin sensitivity was determined: (i) in the fast state; (ii) after a standardized test meal; (iii) after GSH + NO; and after (iv) S-nitrosoglutathione (GSNO) administration. The fasting glucose level was not different between the control and high-sucrose group. In the liver, the high-sucrose model shows increased NO and unchanged GSH levels. In control animals, insulin sensitivity increased after a meal or administration of GSH+NO/GSNO, but this was abrogated by sucrose feeding. GSNO was able to revert insulin resistance induced by sucrose feeding, in a dose-dependent manner, suggesting that they have an insulin-sensitizing effect in vivo. These effects are associated with an increased insulin receptor and Akt phosphorylation in muscle cells. Our findings demonstrate that GSNO promotes insulin sensitivity in a sucrose-induced insulin-resistant animal model and further implicates that this antioxidant molecule may act as a potential pharmacological tool for the treatment of insulin resistance in obesity and type 2 diabetes.

Arctiin attenuates high glucose-induced human retinal capillary endothelial cell proliferation by regulating ROCK1/PTEN/PI3K/Akt/VEGF pathway in vitro

Diabetic retinopathy (DR) is one of the most prominent microvascular complications of diabetes, which remains the leading cause of legal blindness in the world. Arctiin, a bioactive compound from Arctium lappa L., has been reported to have antidiabetic activity. In this study, we investigated the effect of arctiin on a human retinal capillary endothelial cell (HRCEC) line and how arctiin inhibits cell proliferation in high glucose (HG)-induced HRCECs. Results showed that arctiin decreased HG-induced HRCECs proliferation in a dose-dependent manner by inducing cell cycle arrest at the G0/G1 phase. Tube formation assay and immunofluorescence staining indicated that arctiin abrogated tube formation induced by HG-induced HRCECs in a dose-dependent manner via down-regulation of VEGF expression. Mechanistic study indicated that perturbation of the ROCK1/PTEN/PI3K/Akt signalling pathway plays a vital role in the arctiin-mediated anti-proliferative effect. Furthermore, pre-incubation of HRCECs with Y-27632 attenuated arctiin-induced cell cycle arrest, cell proliferation and tube formation inhibition. Y-27632 also reversed the activation of PTEN, the inactivation/dephosphorylation of PI3K/Akt and down-regulation of VEGF. Taken together, the results demonstrated that arctiin inhibits the proliferation of HG-induced HRCECs through the activation of ROCK1 and PTEN and inactivation of PI3K and Akt, resulting in down-regulation of VEGF, which inhibits endothelial cell proliferation.

Clark C, Celka R. A Review of Exercise as Medicine in Cardiovascular Disease: Pathology and Mechanism

BACKGROUND

Physical inactivity and resultant lower energy expenditure contribute unequivocally to cardiovascular diseases, such as coronary artery disease and stroke, which are considered major causes of disability and mortality worldwide.

AIM

The aim of the study was to investigate the influence of physical activity (PA) and exercise on different aspects of health - genetics, endothelium function, blood pressure, lipid concentrations, glucose intolerance, thrombosis, and self - satisfaction. Materials and.

METHODS

In this article, we conducted a narrative review of the influence PA and exercise have on the cardiovascular system, risk factors of cardiovascular diseases, searching the online databases; Web of Science, PubMed and Google Scholar, and, subsequently, discuss possible mechanisms of this action.

RESULTS AND DISCUSSION

Based on our narrative review of literature, discussed the effects of PA on telomere length, nitric oxide synthesis, thrombosis risk, blood pressure, serum glucose, cholesterol and triglycerides levels, and indicated possible mechanisms by which physical training may lead to improvement in chronic cardiovascular diseases.

CONCLUSION

PA is effective for the improvement of exercise tolerance, lipid concentrations, blood pressure, it may also reduce the serum glucose level and risk of thrombosis, thus should be advocated concomitant to, or in some cases instead of, traditional drug-therapy.

Rho-ROCK Signaling in Normal Physiology and as a Key Player in Shaping the Tumor Microenvironment

The Rho-ROCK signaling network has a range of specialized functions of key biological importance, including control of essential developmental processes such as morphogenesis and physiological processes including homeostasis, immunity, and wound healing. Deregulation of Rho-ROCK signaling actively contributes to multiple pathological conditions, and plays a major role in cancer development and progression. This dynamic network is critical in modulating the intricate communication between tumor cells, surrounding diverse stromal cells and the matrix, shaping the ever-changing microenvironment of aggressive tumors. In this chapter, we overview the complex regulation of the Rho-ROCK signaling axis, its role in health and disease, and analyze progress made with key approaches targeting the Rho-ROCK pathway for therapeutic benefit. Finally, we conclude by outlining likely future trends and key questions in the field of Rho-ROCK research, in particular surrounding Rho-ROCK signaling within the tumor microenvironment.

Physical exercise increases ROCK activity in the skeletal muscle of middle-aged rats

The physical exercise is a potential strategy to control age-related metabolic disorders, such as insulin resistance, impaired glucose homeostasis, and type 2 diabetes. Rho-kinase (ROCK) increases skeletal muscle glucose uptake through Insulin Receptor Substrate 1 (IRS1) phosphorylation. Here, we investigated the role of physical exercise in ROCK pathway in the skeletal muscle of Fischer middle-aged rats. Firstly, we observed the ROCK distribution in different skeletal muscle fiber types. ROCK signaling pathway (ROCK1 and ROCK2) and activity (pMYPT1) were higher in the soleus, which was associated with increased insulin signaling pathway (pIR, pIRS1, pPDK, pGSK3β). Middle-aged rats submitted to physical exercise, showed the upregulation of ROCK2 content and normalized RhoA (ROCK activator enzyme) levels in soleus muscle compared with middle-aged sedentary rats. These molecular changes in middle-aged exercised rats were accompanied by higher insulin signaling (pIRS1, pGSK3β, pAS160, GLUT4) in the soleus muscle. Reinforcing these findings, when pharmacological inhibition of ROCK activity was performed (using Y-27632), the insulin signaling pathway and glucose metabolism-related genes (Tpi, Pgk1, Pgam2, Eno3) were decreased in the soleus muscle of exercised rats. In summary, ROCK signaling seems to contribute with whole-body glucose homeostasis (∼50 %) through its higher upregulation in the soleus muscle in middle-aged exercised rats.

Tissue-Specific Approaches Reveal Diverse Metabolic Functions of Rho-Kinase 1

Rho-kinase 1 (ROCK1) has been implicated in diverse metabolic functions throughout the body, with promising evidence identifying ROCK1 as a therapeutic target in diabetes and obesity. Considering these metabolic roles, several pharmacological inhibitors have been developed to elucidate the mechanisms underlying ROCK1 function. Y27632 and fasudil are two common ROCK1 inhibitors; however, they have varying non-specific selectivity to inhibit other AGC kinase subfamily members and whole-body pharmacological approaches lack tissue-specific insight. As a result, interpretation of studies with these inhibitors is difficult, and alternative approaches are needed to elucidate ROCK1's tissue specific metabolic functions. Fortunately, recent technological advances utilizing molecular carriers or genetic manipulation have facilitated discovery of ROCK1's tissue-specific mechanisms of action. In this article, we review the tissue-specific roles of ROCK1 in the regulation of energy balance and substrate utilization. We highlight prominent metabolic roles in liver, adipose, and skeletal muscle, in which ROCK1 regulates energy expenditure, glucose uptake, and lipid metabolism via inhibition of AMPK2α and paradoxical modulation of insulin signaling. Compared to ROCK1's roles in peripheral tissues, we also describe contradictory functions of ROCK1 in the hypothalamus to increase energy expenditure and decrease food intake via leptin signaling. Furthermore, dysregulated ROCK1 activity in either of these tissues results in metabolic disease phenotypes. Overall, tissue-specific approaches have made great strides in deciphering the many critical metabolic functions of ROCK1 and, ultimately, may facilitate the development of novel treatments for metabolic disorders.

ROCK2 inhibition enhances the thermogenic program in white and brown fat tissue in mice

The RhoA/ROCK-mediated actin cytoskeleton dynamics have been implicated in adipogenesis. The two ROCK isoforms, ROCK1 and ROCK2, are highly homologous. The contribution of ROCK2 to adipogenesis in vivo has not been elucidated. The present study aimed at the in vivo and in vitro roles of ROCK2 in the regulation of adipogenesis and the development of obesity. We performed molecular, histological, and metabolic analyses in ROCK2^+/- and ROCK2^+/KD mouse models, the latter harboring an allele with a kinase-dead (KD) mutation. Both ROCK2^+/- and ROCK2^+/KD mouse models showed a lean body mass phenotype during aging, associated with increased amounts of beige cells in subcutaneous white adipose tissue (sWAT) and increased thermogenic gene expression in all fat depots. ROCK2^+/- mice on a high-fat diet showed increased energy expenditure accompanying by reduced obesity, and improved insulin sensitivity. In vitro differentiated ROCK2^+/- stromal-vascular (SV) cells revealed increased beige adipogenesis associated with increased thermogenic gene expressions. Treatment with a selective ROCK2 inhibitor, KD025, to inhibit ROCK2 activity in differentiated SV cells reproduced the pro-beige phenotype of ROCK2^+/- SV cells. In conclusion, ROCK2 activity-mediated actin cytoskeleton dynamics contribute to the inhibition of beige adipogenesis in WAT, and also promotes age-related and diet-induced fat mass gain and insulin resistance.

Rock protein as cardiac hypertrophy modulator in obesity and physical exercise

Obesity and cardiovascular diseases are worldwide public health issues. In this review, we discussed the participation of ROCK protein in cardiac hypertrophy, mainly through the modulation of leptin and insulin signaling pathways. Leptin plays a role in cardiovascular disease development and, through the Rho-associated protein kinase (ROCK), promotes cardiac hypertrophy. ROCK protein, is regulated by small Rho-GTPases and has two isoforms with high homology. ROCK is able to activate the MAP kinase (MAPK) pathway and modulate insulin signaling in the heart, participating in cardiac hypertrophy development of concentric and eccentric left ventricle growth. Although different types of stimulus can lead to morphologically antagonistic heart growth, physical exercise promotes improvements in hemodynamic function, emerging as a promising non-pharmacological tool to improve overall health. Leptin can activate ROCK in a pathological way, increasing MAPK activity and decreasing insulin signaling via insulin receptor substrate 1 (IRS1) serine 307 residue phosphorylation, phosphatase and tensin homolog, and protein kinase Cβ2. In turn, physical exercise decreases leptin levels and positively modulates insulin signaling as well as increases ROCK-dependent IRS1 (Ser632/635) phosphorylation, improving phosphatidylinositol 3-kinase/protein kinase B axis and promoting physiologic heart growth. Currently, there is a lack of studies about differences in ROCK isoforms, especially during exercise and/or obesity. However, the understanding of its biological function and the complex mechanism underlying the distinct types of cardiac hypertrophy development can be a useful tool in the improvement and treatment of cardiovascular outcomes.

Regulation of glucose transport by RhoA in 3T3-L1 adipocytes and L6 myoblasts

RhoA is a key player in actin cytoskeleton reorganization and exerts most of its effect through the RhoA-ROCKs signaling pathway. Although recent studies have stressed the roles of ROCKs as regulators of glucose metabolism, little is known of the roles played by RhoA, the upstream regulators of ROCKs and other isotypes of Rho small-GTPases. This study was undertaken to determine whether Rho isotypes modulate glucose transport and insulin signaling in insulin-sensitive cell models, that is, 3T3-L1 adipocytes and L6 myoblasts. Glucose uptake assays showed that RhoA knockdown using siRNA reduced insulin-stimulated glucose transport in both cell types, whereas knockdown of RhoB or RhoC did not. Furthermore, RhoA overexpression increased insulin-stimulated glucose transport. Interestingly, the insulin-stimulated PI3K-Akt signaling pathway was unaffected under RhoA-depleted or -overexpressed conditions, which suggested RhoA might regulate glucose transport via an Akt-independent pathway. Interestingly, an immunoblot assay of signaling molecules related to actin-myosin cytoskeletal remodeling showed that unlike RhoA or RhoC, RhoA regulated ERM phosphorylation. Our results suggest that RhoA, but not RhoB or RhoC, mediates glucose transport by regulating the vesicle trafficking machinery in an Akt-independent manner.

Adipose cell size changes are associated with a drastic actin remodeling

Adipose tissue plays a major role in regulating whole-body insulin sensitivity and energy metabolism. To accommodate surplus energy, the tissue rapidly expands by increasing adipose cell size (hypertrophy) and cell number (hyperplasia). Previous studies have shown that enlarged, hypertrophic adipocytes are less responsive to insulin, and that adipocyte size could serve as a predictor for the development of type 2 diabetes. In the present study, we demonstrate that changes in adipocyte size correlate with a drastic remodeling of the actin cytoskeleton. Expansion of primary adipocytes following 2 weeks of high-fat diet (HFD)-feeding in C57BL6/J mice was associated with a drastic increase in filamentous (F)-actin as assessed by fluorescence microscopy, increased Rho-kinase activity, and changed expression of actin-regulating proteins, favoring actin polymerization. At the same time, increased cell size was associated with impaired insulin response, while the interaction between the cytoskeletal scaffolding protein IQGAP1 and insulin receptor substrate (IRS)-1 remained intact. Reversed feeding from HFD to chow restored cell size, insulin response, expression of actin-regulatory proteins and decreased the amount of F-actin filaments. Together, we report a drastic cytoskeletal remodeling during adipocyte expansion, a process which could contribute to deteriorating adipocyte function.

Rho GTPases-Emerging Regulators of Glucose Homeostasis and Metabolic Health

Rho guanosine triphosphatases (GTPases) are key regulators in a number of cellular functions, including actin cytoskeleton remodeling and vesicle traffic. Traditionally, Rho GTPases are studied because of their function in cell migration and cancer, while their roles in metabolism are less documented. However, emerging evidence implicates Rho GTPases as regulators of processes of crucial importance for maintaining metabolic homeostasis. Thus, the time is now ripe for reviewing Rho GTPases in the context of metabolic health. Rho GTPase-mediated key processes include the release of insulin from pancreatic β cells, glucose uptake into skeletal muscle and adipose tissue, and muscle mass regulation. Through the current review, we cast light on the important roles of Rho GTPases in skeletal muscle, adipose tissue, and the pancreas and discuss the proposed mechanisms by which Rho GTPases act to regulate glucose metabolism in health and disease. We also describe challenges and goals for future research.

Eph signaling controls mitotic spindle orientation and cell proliferation in neuroepithelial cells

In this study, Franco and Carmena uncover a function for Eph signaling as a novel extrinsic mechanism controlling mitotic spindle alignment in Drosophila neuroepithelial cells through aPKC activity–dependent myosin II regulation. Additionally, Eph loss leads to a Rho signaling–dependent activation of the PI3K–Akt1 pathway, enhancing cell proliferation within this neuroepithelium.

Mitotic spindle orientation must be tightly regulated during development and adult tissue homeostasis. It determines cell-fate specification and tissue architecture during asymmetric and symmetric cell division, respectively. Here, we uncover a novel role for Ephrin–Eph intercellular signaling in controlling mitotic spindle alignment in Drosophila optic lobe neuroepithelial cells through aPKC activity–dependent myosin II regulation. We show that conserved core components of the mitotic spindle orientation machinery, including Discs Large1, Mud/NuMA, and Canoe/Afadin, mislocalize in dividing Eph mutant neuroepithelial cells and produce spindle alignment defects in these cells when they are down-regulated. In addition, the loss of Eph leads to a Rho signaling–dependent activation of the PI3K–Akt1 pathway, enhancing cell proliferation within this neuroepithelium. Hence, Eph signaling is a novel extrinsic mechanism that regulates both spindle orientation and cell proliferation in the Drosophila optic lobe neuroepithelium. Similar mechanisms could operate in other Drosophila and vertebrate epithelia.

Transgenerational Obesity and Alteration of ARHGEF11 in the Rat Liver Induced by Intrauterine Hyperglycemia

It is understood that intrauterine hyperglycemia increases the risk of obesity and diabetes in offspring of consecutive generations but its mechanisms remain obscure. This study is aimed at establishing an intrauterine hyperglycemia rat model to investigate the growth and glycolipid metabolic characteristics in transgenerational offspring and discuss the effects of Rho guanine nucleotide exchange factor 11 (ARHGEF11) and the PI3K/AKT signaling pathway in offspring development. The severe intrauterine hyperglycemia rat model was caused by STZ injection before mating, while offspring development and glycolipid metabolism were observed for the following two generations. The expression of ARHGEF11, ROCK1, PI3K, and AKT was tested in the liver and muscle tissue of F2 offspring. The results showed severe growth restriction in F1 offspring and obesity, fatty liver, and insulin resistance in female F2 offspring, especially the offspring of female intrauterine hyperglycemia-exposed parents (F2G♀C♂) and both (F2G♀G♂). The expression of ARHGEF11 and ROCK1 was significantly elevated; PI3K and phosphorylation of AKT were significantly decreased in liver tissues of F2G♀C♂ and F2G♀G♂. Our study revealed that intrauterine hyperglycemia could cause obesity and abnormal glycolipid metabolism in female transgenerational offspring; the programming effect of the intrauterine environment could cause a more obvious phenotype in the maternal line. Further exploration suggested that increased expression of ARHGEF11 and ROCK1 and the decreased expression of PI3K and phosphorylation of AKT in the liver could be responsible for the abnormal development in F2 offspring.

The role of sphingosine-1-phosphate in skeletal muscle: Physiology, mechanisms, and clinical perspectives

Sphingolipids were discovered more than a century ago and were simply considered as a class of cell membrane lipids for a long time. However, after the discovery of several intracellular functions and their role in the control of many physiological and pathophysiological conditions, these molecules have gained much attention. For instance, the sphingosine-1-phosphate (S1P) is a circulating bioactive sphingolipid capable of triggering strong intracellular reactions through the family of S1P receptors (S1PRs) spread in several cell types and tissues. Recently, the role of S1P in the control of skeletal muscle metabolism, atrophy, regeneration, and metabolic disorders has been widely investigated. In this review, we summarized the knowledge of S1P and its effects in skeletal muscle metabolism, highlighting the role of S1P/S1PRs axis in skeletal muscle regeneration, fatigue, ceramide accumulation, and insulin resistance. Finally, we discussed the physical exercise role in S1P/S1PRs signaling in skeletal muscle cells, and how this nonpharmacological strategy may be prospective for future investigations due to its ability to increase S1P levels.

Rho-kinase/AMPK axis regulates hepatic lipogenesis during overnutrition

Obesity is a major risk factor for developing nonalcoholic fatty liver disease (NAFLD). NAFLD is the most common form of chronic liver disease and is closely associated with insulin resistance, ultimately leading to cirrhosis and hepatocellular carcinoma. However, knowledge of the intracellular regulators of obesity-linked fatty liver disease remains incomplete. Here we showed that hepatic Rho-kinase 1 (ROCK1) drives obesity-induced steatosis in mice through stimulation of de novo lipogenesis. Mice lacking ROCK1 in the liver were resistant to diet-induced obesity owing to increased energy expenditure and thermogenic gene expression. Constitutive expression of hepatic ROCK1 was sufficient to promote adiposity, insulin resistance, and hepatic lipid accumulation in mice fed a high-fat diet. Correspondingly, liver-specific ROCK1 deletion prevented the development of severe hepatic steatosis and reduced hyperglycemia in obese diabetic (ob/ob) mice. Of pathophysiological significance, hepatic ROCK1 was markedly upregulated in humans with fatty liver disease and correlated with risk factors clustering around NAFLD and insulin resistance. Mechanistically, we found that hepatic ROCK1 suppresses AMPK activity and a ROCK1/AMPK pathway is necessary to mediate cannabinoid-induced lipogenesis in the liver. Furthermore, treatment with metformin, the most widely used antidiabetes drug, reduced hepatic lipid accumulation by inactivating ROCK1, resulting in activation of AMPK downstream signaling. Taken together, our findings establish a ROCK1/AMPK signaling axis that regulates de novo lipogenesis, providing a unique target for treating obesity-related metabolic disorders such as NAFLD.

Glucagon-like peptide-1 ameliorates cardiac lipotoxicity in diabetic cardiomyopathy via the PPARα pathway

Lipotoxicity cardiomyopathy is the result of excessive accumulation and oxidation of toxic lipids in the heart. It is a major threat to patients with diabetes. Glucagon-like peptide-1 (GLP-1) has aroused considerable interest as a novel therapeutic target for diabetes mellitus because it stimulates insulin secretion. Here, we investigated the effects and mechanisms of the GLP-1 analog exendin-4 and the dipeptidyl peptidase-4 inhibitor saxagliptin on cardiac lipid metabolism in diabetic mice (DM). The increased myocardial lipid accumulation, oxidative stress, apoptosis, and cardiac remodeling and dysfunction induced in DM by low streptozotocin doses and high-fat diets were significantly reversed by exendin-4 and saxagliptin treatments for 8 weeks. We found that exendin-4 inhibited abnormal activation of the (PPARα)-CD36 pathway by stimulating protein kinase A (PKA) but suppressing the Rho-associated protein kinase (ROCK) pathway in DM hearts, palmitic acid (PA)-treated rat h9c2 cardiomyocytes (CMs), and isolated adult mouse CMs. Cardioprotection in DM mediated by exendin-4 was abolished by combination therapy with the PPARα agonist wy-14643 but mimicked by PPARα gene deficiency. Therefore, the PPARα pathway accounted for the effects of exendin-4. This conclusion was confirmed in cardiac-restricted overexpression of PPARα mediated by adeno-associated virus serotype-9 containing a cardiac troponin T promoter. Our results provide the first direct evidence that GLP-1 protects cardiac function by inhibiting the ROCK/PPARα pathway, thereby ameliorating lipotoxicity in diabetic cardiomyopathy.

Loss of CLOCK under high glucose upregulates ROCK1-mediated endothelial to mesenchymal transition and aggravates plaque vulnerability

BACKGROUND AND AIMS

Carotid atherosclerotic plaque is one of the main sources of ischemic stroke, and endothelial-to-mesenchymal transition (EndMT) is a major feature of atherosclerosis. Rho-associated coiled-coil-containing protein kinase 1 (ROCK1) activation, stimulated by high glucose, plays an important role in EndMT, and circadian locomotor output cycles protein kaput (Clock) deficiency leads to hyperglycemia and enhanced atherosclerosis in Clock^Δ19/Δ19apolipoprotein E (ApoE)^-/- mice. These findings point to a mechanism whereby CLOCK exerts a protective effect against EndMT and atherosclerotic plaque accumulation.

METHODS

Cultured human umbilical vein endothelial cells (HUVECs) were stimulated with 66 mM glucose for 120 h to induce EndMT. The expression of CLOCK and ROCK1 was assayed, as were their effects on EndMT. We also conducted molecular and morphometric examination of carotid artery plaques from patients with carotid artery stenosis to assess the clinical relevance of these findings.

RESULTS

Upon EndMT, HUVECs exhibited decreased CLOCK expression and increased ROCK1 expression. Notably, CLOCK silencing increased high glucose-induced EndMT, migration ability, and ROCK1 activation, while overexpressing CLOCK attenuated these characteristics. Moreover, inhibition of ROCK1 largely blocked EndMT induced by high-glucose or transforming growth factor (TGF)-β1 but failed to rescue the reduced CLOCK expression. The vulnerability of human carotid artery plaque was strongly correlated with loss of CLOCK expression, activation of TGF-β/ROCK1 signaling, and the extent of EndMT.

CONCLUSIONS

The data indicate that loss of protective endothelial CLOCK expression aggravates TGF-β/ROCK1-modulated EndMT progression, which contributes to the vulnerability of human carotid plaque.

Regulation of RhoA GTPase and novel target proteins for ROCK

Rho GTPases play significant roles in cellular function and their activity is regulated by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs), providing activation and inactivation of these GTPases, respectively. Active GTP-bound form of RhoA activates its effector proteins while the inactive GDP-bound form of RhoA exists in a RhoA-RhoGDI (guanine nucleotide dissociation inhibitor) complex in the cytosol. In particular, IκB kinase γ IKKγ/NF-κB essential modulator (NEMO) plays a role as a GDI displacement factor (GDF) for RhoA activation through binding to RhoA-RhoGDI complex. Meanwhile, prion protein inactivates RhoA despite RhoA/RhoGDI association. Novel target proteins for Rho-associated kinase (ROCK) such as glycogen synthase kinase (GSK)-3β and IKKβ are recently discovered. Here, we elaborate on a post-translationally modified version of RhoA, phosphorylated at Tyr42 and oxidized at Cys16/20. This form of RhoA dissociates from RhoA-RhoGDI complex and activates IKKβ on IKKγ/NEMO, thus providing possibly a critical role for tumourigenesis.

Protein kinase N2 regulates AMP kinase signaling and insulin responsiveness of glucose metabolism in skeletal muscle

Insulin resistance is central to the development of type 2 diabetes and related metabolic disorders. Because skeletal muscle is responsible for the majority of whole body insulin-stimulated glucose uptake, regulation of glucose metabolism in this tissue is of particular importance. Although Rho GTPases and many of their affecters influence skeletal muscle metabolism, there is a paucity of information on the protein kinase N (PKN) family of serine/threonine protein kinases. We investigated the impact of PKN2 on insulin signaling and glucose metabolism in primary human skeletal muscle cells in vitro and mouse tibialis anterior muscle in vivo. PKN2 knockdown in vitro decreased insulin-stimulated glucose uptake, incorporation into glycogen, and oxidation. PKN2 siRNA increased 5'-adenosine monophosphate-activated protein kinase (AMPK) signaling while stimulating fatty acid oxidation and incorporation into triglycerides and decreasing protein synthesis. At the transcriptional level, PKN2 knockdown increased expression of PGC-1α and SREBP-1c and their target genes. In mature skeletal muscle, in vivo PKN2 knockdown decreased glucose uptake and increased AMPK phosphorylation. Thus, PKN2 alters key signaling pathways and transcriptional networks to regulate glucose and lipid metabolism. Identification of PKN2 as a novel regulator of insulin and AMPK signaling may provide an avenue for manipulation of skeletal muscle metabolism.

Suppression of Rho-kinase 1 is responsible for insulin regulation of the AMPK/SREBP-1c pathway in skeletal muscle cells exposed to palmitate

AIMS

Clinical and experimental data suggest that early insulin therapy could reduce lipotoxicity in subjects and animal models with type 2 diabetes mellitus. However, the underlying mechanisms need to be clarified. Sterol regulatory element-binding protein 1c (SREBP-1c), which is negatively regulated by AMP-activated protein kinase (AMPK), plays a critical role in lipotoxicity and insulin resistance in skeletal muscle cells. Here, we investigated the effect and molecular mechanism of insulin intervention on the AMPK/SREBP-1c pathway in skeletal muscle cells with chronic exposure to palmitic acid (PA).

METHODS

Male C57BL/6 mice were fed with a high-fat diet for 12 weeks and were then treated with insulin, AMPK inhibitor, or metformin. L6 myotubes incubated with palmitic acid (PA) were treated with insulin or metformin. Dominant-negative AMPKα2 (DN-AMPKα2) lentivirus, AMPKα2 siRNA, or Rho-kinase 1 (ROCK1) siRNA were transfected into PA-treated L6 myotubes.

RESULTS

We found that the ability of PA to stimulate SREBP-1c and inhibit AMPK was reversed by insulin in L6 cells. Moreover, DN-AMPKα2 lentivirus and AMPKα2 siRNA were transfected into PA-treated L6 myotubes, and the decrease in SREBP-1c expression caused by insulin was blocked by AMPK inhibition independent of the phosphatidylinositol-4,5-biphosphate-3-kinase (PI3K)/AKT pathway. The serine/threonine kinase Rho-kinase (ROCK) 1, a downstream effector of the small G protein RhoA, was activated by PA. Interestingly, knockdown of ROCK1 by siRNA blocked the downregulation of AMPK phosphorylation under PA-treated L6 myotubes, which indicated that ROCK1 mediated the effect of insulin action on AMPK.

CONCLUSIONS

Our study indicated that insulin reduced lipotoxicity via ROCK1 and then improved AMPK/SREBP-1c signaling in skeletal muscle under PA-induced insulin resistance.

New association of bone morphogenetic protein 4 concentrations with fat distribution in obesity and Exenatide intervention on it

Background

Bone morphogenetic protein 4 (BMP-4) has been proven to regulate white adipogensis. We aimed to demonstrate the correlation of BMP-4 with fat distribution and Exenatide treatment on it.

Methods

We enrolled 69 obese patients. Anthropometric and metabolic indexes were collected. Fat distribution was measured by dual-energy X-ray absorptiometry. BPM-4 levels were assessed using enzyme-link immunosorbent assay kit. 30 obese patients were treated with Exenatide twice a day. Change in body weight, metabolic-related indices and BPM-4 levels were evaluated after 18 weeks.

Results

1) The mean(±SD) BMP-4 levels were 763.98 ± 324.11 pg/ml in the obese. BPM-4 levels were significantly positively correlated with estimated visceral adipose tissue mass in all subjects and also in females (r = 0.377, r = 0.625, respectively,all P < 0.05). BPM-4 levels were also significantly positively correlated with body mass index, hip circumference and total fat% in females (r = 0.375,r = 0.429,r = 0.493,respectively, all P < 0.05). BPM-4 levels were negatively correlated with total cholesterol(TC) in all subjects and males also (r = −0.373,r = −0.332,respectively, all P < 0.05). BPM-4 levels were also significantly positively correlated with free triiodothyronine in males (r = 0.441, P < 0.05). 3) Multivariate analyses showed that TC was risk factor of BMP-4 concentration in males and Est.VAT Area was risk factor of BMP-4 levels in females. 4) BMP-4 levels were significantly higher in the obesity with slightly increased thyroid stimulating hormone(TSH) than the obesity without slightly increased TSH (902.08 ± 354.74 pg/ml vs. 720.24 ± 306.41 pg/ml, P < 0.05). 5) Exenatide treatment leads to a significant decreased in BMP-4 from 860.05 ± 352.65 pg/ml to 649.44 + 277.49 pg/ml independent of weight loss(P < 0.05).

Conclusion

BMP-4 levels were associated with the visceral adipose tissue and may play a certain role in fat distribution and subclinical hypothyroidism in obesity. Exenatide treatment reduced BMP-4 levels independent of weight loss.

Trial registration

Clinicaltrials.gov Identifier: NCT02118376, Registered 16 April.

Methylsulfonylmethane (MSM), an organosulfur compound, is effective against obesity-induced metabolic disorders in mice

Methylsulfonylmethane (MSM), an organosulfur compound, has been used as a dietary supplement that can improve various metabolic diseases. However, the effect of MSM on obesity-linked metabolic disorders remains unclear. The goal of the current study is to determine whether MSM has beneficial effects on glucose and lipid homeostasis in obesity-associated pathophysiologic states. High-fat diet-induced obese (DIO) and genetically obese diabetic db/db mice treated with MSM (1%-5% v/v, by drinking water) were studied. Metabolic parameters involved in glucose and lipid metabolism were determined. Treatment of DIO mice with MSM leads to a significant decrease in blood glucose levels. DIO mice treated with MSM are hypersensitive to insulin, as evidenced by decreased serum insulin and an increase in the area above the curve during an ITT. Concurrently, MSM reduces hepatic triglyceride and cholesterol contents in DIO mice. These effects are accompanied by reductions in gene expression of key molecules involved in lipogenesis and inflammation. FACS analysis reveals that MSM markedly increases the frequency of B cells and decreases the frequency of myeloid cells in peripheral blood and in bone marrow. Moreover, overnutrition-induced changes of femur microarchitecture are restored by MSM. In db/db mice, a marked impairment in glucose and lipid metabolic profiles is notably ameliorated when MSM is supplemented. These data suggest that MSM has beneficial effects on multiple metabolic dysfunctions, including hyperglycemia, hyperinsulinemia, insulin resistance, and inflammation. Thus, MSM could be the therapeutic option for the treatment of obesity-related metabolic disorders such as type 2 diabetes and fatty liver diseases.

Enhanced Rho-kinase activity: Pathophysiological relevance in type 2 diabetes

BACKGROUND

Accumulating evidence indicates that Rho-associated kinase (ROCK) has been involved in the pathogenesis of insulin resistance and diabetes. However, little clinical evidence for ROCK activity in diabetic patients is available. We determined whether ROCK activity is systemically enhanced in type 2 diabetic patients and associated with other components of diabetes.

METHODS

Seventy-eight volunteers, including 41 type 2 diabetic patients and 37 control subjects, were participated in this study. Fasting blood samples were collected to measure ROCK activity in circulating leukocyte, determined by the ratio of phosphorylation/total myosin-binding subunit (MBS), a direct downstream target of ROCK.

RESULTS

Compared with the control subjects, ROCK activity was significantly increased in type 2 diabetic patients (phosphorylation/total MBS ratio 0.80±0.10 vs. 0.72±0.08, P<0.01). An independent positive correlation was found between ROCK activity and HbA_1c concentration in type 2 diabetic patients but not in control subjects (r=0.40, P=0.01). In multiple regression analysis, ROCK activity remains associated significantly in a positive manner with HbA_1c concentration in type 2 diabetes (β=0.03, P=0.04).

CONCLUSIONS

These findings demonstrated that ROCK activity is significantly increased in type 2 diabetic patients and enhanced ROCK activity may reflect the progression of disease.

ROCK1 reduces mitochondrial content and irisin production in muscle suppressing adipocyte browning and impairing insulin sensitivity

Irisin reportedly promotes the conversion of preadipocytes into "brown-like" adipocytes within subcutaneous white adipose tissue (WAT) via a mechanism that stimulates UCP-1 expression. An increase in plasma irisin has been associated with improved obesity and insulin resistance in mice with type 2 diabetes. But whether a low level of irisin stimulates the development of obesity has not been determined. In studying mice with muscle-specific constitutive ROCK1 activation (mCaROCK1), we found that irisin production was down-regulated and the mice developed obesity and insulin resistance. Therefore, we studied the effects of irisin deficiency on energy metabolism in mCaROCK1 mice. Constitutively activation of ROCK1 in muscle suppressed irisin expression in muscle resulting in a low level of irisin in circulation. Irisin deficiency reduced heat production and decreased the expression of uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) and subcutaneous WAT. Moreover, mCaROCK1 mice also displayed impaired glucose tolerance. Notably, irisin replenishment in mCaROCK1 mice partially reversed insulin resistance and obesity and these changes were associated with increased expression of UCP1 and Pref-1 in subcutaneous WAT. These results demonstrate that irisin mediates muscle-adipose tissue communication and regulates energy and glucose homeostasis. Irisin administration can correct obesity and insulin resistance in mice.