JAK-STAT signaling and myocardial glucose metabolism

Single oral administration of quercetin glycosides prevented acute hyperglycemia by promoting GLUT4 translocation in skeletal muscles through the activation of AMPK in mice

Quercetin is a natural flavonol and has various health beneficial functions. Our pervious study demonstrated that long-term feeding (13 weeks) of quercetin and its glycosides, isoquercitrin, rutin, and enzymatically modified isoquercitrin, which is a mixture of quercetin monoglycoside and its oligoglycosides, prevented hyperglycemia and adiposity in mice fed a high-fat diet but not standard diet. It is, however, unclear whether a single administration of these compounds prevent postprandial hyperglycemia or not. In the present study, we estimated their prevention effect on acute hyperglycemia by an oral glucose tolerance test in ICR mice and investigated its mechanism. It was found that quercetin glycosides, but not the aglycone, suppressed acute hyperglycemia and isoquercitrin showed the strongest effect among the glycosides. As the underlying mechanism, quercetin glycosides promoted translocation of glucose transporter 4 to the plasma membrane of skeletal muscle of mice through phosphorylation of adenosine monophosphate-activated protein kinase and its upstream Ca2+/calmodulin-dependent protein kinase kinase β without activating the insulin- and JAK/STAT-signal pathways. In conclusion, single oral administration of quercetin glycosides prevented a blood sugar spike by promoting glucose transporter 4 translocation through activating the CAMKKβ/AMPK signaling pathway.

Insulin-mediated endothelin signaling is antiviral during West Nile virus infection

IMPORTANCE

Arboviruses, particularly those transmitted by mosquitoes, pose a significant threat to humans and are an increasing concern because of climate change, human activity, and expanding vector-competent populations. West Nile virus is of significant concern as the most frequent mosquito-borne disease transmitted annually within the continental United States. Here, we identify a previously uncharacterized signaling pathway that impacts West Nile virus infection, namely endothelin signaling. Additionally, we demonstrate that we can successfully translate results obtained from D. melanogaster into the more relevant human system. Our results add to the growing field of insulin-mediated antiviral immunity and identify potential biomarkers or intervention targets to better address West Nile virus infection and severe disease.

Recent advances in JAK inhibitors for the treatment of metabolic syndrome

With an epidemic spread, metabolic syndrome represents an increasingly emerging risk for the population globally, and is currently recognized as a pathological entity. It is represented by a cluster of different conditions including increased blood pressure, high blood sugar, excess body fat around the waist and abnormal cholesterol or triglyceride levels. These conditions lead directly to several disorders, including obesity, dyslipidemia, hyperglycaemia, insulin resistance, impaired glucose tolerance and hypertension causing an increase in cardiovascular risk and in particular atherosclerotic disease. Despite efforts to promote healthier lifestyles through exercise, reduced caloric intake, and improved dietary choices, the incidence and prevalence of metabolic syndrome continue to rise worldwide. Recent research has highlighted the involvement of signaling pathways in chronic inflammatory conditions like obesity and type 2 diabetes mellitus, revealing the significance of the JAK/STAT pathway in atherosclerotic events. This pathway serves as a rapid membrane-to-nucleus signaling module that regulates the expression of critical mediators. Consequently, JAK inhibitors (JAKi) have emerged as potential therapeutic options for metabolic diseases, offering a promising avenue for intervention. The aim of this review is to shed light on the emerging indications of JAK inhibitors in metabolic syndrome, emphasizing their potential role in attenuating associated inflammatory processes, improving insulin sensitivity, and addressing cross-talk with the insulin pathway, with the intention of contributing to efforts in the field of inflammation pharmacology.

Insulin-mediated endothelin signaling is antiviral during West Nile virus infection

West Nile virus (WNV) is the most prevalent mosquito-borne virus in the United States with approximately 2,000 cases each year. There are currently no approved human vaccines and a lack of prophylactic and therapeutic treatments. Understanding host responses to infection may reveal potential intervention targets to reduce virus replication and disease progression. The use of Drosophila melanogaster as a model organism to understand innate immunity and host antiviral responses is well established. Previous studies revealed that insulin-mediated signaling regulates WNV infection in invertebrates by regulating canonical antiviral pathways. Because insulin signaling is well-conserved across insect and mammalian species, we sought to determine if results using D. melanogaster can be extrapolated for the analysis of orthologous pathways in humans. Here, we identify insulin-mediated endothelin signaling using the D. melanogaster model and evaluate an orthologous pathway in human cells during WNV infection. We demonstrate that endothelin signaling reduces WNV replication through the activation of canonical antiviral signaling. Taken together, our findings show that endothelin-mediated antiviral immunity is broadly conserved across species and reduces replication of viruses that can cause severe human disease.

IMPORTANCE

Arboviruses, particularly those transmitted by mosquitoes, pose a significant threat to humans and are an increasing concern because of climate change, human activity, and expanding vector-competent populations. West Nile virus is of significant concern as the most frequent mosquito-borne disease transmitted annually within the continental United States. Here, we identify a previously uncharacterized signaling pathway that impacts West Nile virus infection, namely endothelin signaling. Additionally, we demonstrate that we can successfully translate results obtained from D. melanogaster into the more relevant human system. Our results add to the growing field of insulin-mediated antiviral immunity and identifies potential biomarkers or intervention targets to better address West Nile virus infection and severe disease.

βA1-crystallin regulates glucose metabolism and mitochondrial function in mouse retinal astrocytes by modulating PTP1B activity

βA3/A1-crystallin, a lens protein that is also expressed in astrocytes, is produced as βA3 and βA1-crystallin isoforms by leaky ribosomal scanning. In a previous human proteome high-throughput array, we found that βA3/A1-crystallin interacts with protein tyrosine phosphatase 1B (PTP1B), a key regulator of glucose metabolism. This prompted us to explore possible roles of βA3/A1-crystallin in metabolism of retinal astrocytes. We found that βA1-crystallin acts as an uncompetitive inhibitor of PTP1B, but βA3-crystallin does not. Loss of βA1-crystallin in astrocytes triggers metabolic abnormalities and inflammation. In CRISPR/cas9 gene-edited βA1-knockdown (KD) mice, but not in βA3-knockout (KO) mice, the streptozotocin (STZ)-induced diabetic retinopathy (DR)-like phenotype is exacerbated. Here, we have identified βA1-crystallin as a regulator of PTP1B; loss of this regulation may be a new mechanism by which astrocytes contribute to DR. Interestingly, proliferative diabetic retinopathy (PDR) patients showed reduced βA1-crystallin and higher levels of PTP1B in the vitreous humor.

MiR-324/SOCS3 Axis Protects Against Hypoxia/Reoxygenation-Induced Cardiomyocyte Injury and Regulates Myocardial Ischemia via TNF/NF-κB Signaling Pathway

We aimed at exploring the function of microRNA-324/cytokine signaling 3 (miR-324/SOCS3) axis in hypoxia/reoxygenation (H/R) -induced cardiomyocyte injury and its underlying mechanism. The differential expression genes were analyzed based on the GSE83500 and GSE48060 datasets from the Gene Expression Omnibus (GEO) database. Then, to conduct the function enrichment analysis, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were used. The upstream regulatory microRNAs (miRNAs) of the identified genes were predicted by miRanda, miRWalk, and TargetScan websites. MiR-324 expression was measured with quantitative real-time polymerase chain reaction (qRT-PCR). The target binding of miR-324 and SOCS3 was established by dual-luciferase reporter assay. Cardiomyocyte proliferation was analyzed by cell counting kit-8 (CCK-8) assay, whereas the apoptosis was investigated via flow cytometry. The expression of TNF pathway-related proteins was detected by western blot analysis. SOCS3 was upregulated in patients with myocardial infarction (MI), and function enrichment analyses proved that SOCS3 was enriched in TNF signaling pathway. Moreover, we found that miR-324 was the upstream regulatory miRNA of SOCS3 and negatively regulated SOCS3 expression. MiR-324 was downregulated in cardiomyocytes with H/R-induced injury, inhibiting cell proliferation. In the H/R model, SOCS3 suppresses cardiomyocyte proliferation, which was recovered by miR-324, and induces cell apoptosis, which was repressed by miR-324 via regulating the expression of cleaved caspase-3 and p P38-MAPK. MiR-324 upregulation decreased the protein levels of TNF-α, p-P65, and p-IκBα in cardiomyocytes that suffered from H/R, which was reversed with SOCS3 overexpression. MiR-324/SOCS3 axis could improve the H/R-induced injury of cardiomyocytes via regulating TNF/NF-κB signaling pathway, and this might provide a new therapy strategy for myocardial ischemia.

JLX001 improves myocardial ischemia-reperfusion injury by activating Jak2-Stat3 pathway

AIMS

To investigate the preclinical pharmacodynamics and mechanism of JLX001 against myocardial ischemia reperfusion (MI/R) for clinical application.

MATERIALS AND METHODS

In vivo, SD rats were given intragastric administration for 5 days, and the MI/R model was established by ligating/releasing the left anterior descending coronary artery. In vitro, the oxygen-glucose deprivation/reperfusion (OGD/R) model was established after the drug was pre-incubated for 24 h in H9C2 cells. The infract size was determined by TTC staining. Left ventricular function of MI/R rats was detected by echocardiography. The level of histopathological score was determined by hematoxylin-eosin (HE) staining. The level of superoxide dismutase (SOD), malondialdehyde (MDA), creatine kinase (CK), lactic dehydrogenase (LDH), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) were determined by relevant kits. The level of apoptosis was measured by Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and Hoechst staining. The expression of p-Jak2, p-Stat3, Bax, Bcl-2, TNF-α, IL-1β protein were determined by western blot.

KEY FINDINGS

JLX001 can significantly improve left ventricular function, reduce myocardial infract size, histopathological score, the level of MDA, CK, LDH, TNF-α, IL-1β and the expression of Bax protein, significantly increase the activity of SOD, Bcl-2 protein expression, p-Jak2 protein expression, p-Stat3 protein expression in rat heart tissues and H9C2 cells. These effects can be reversed by AG490 which is a specific inhibitor of Jak2-Stat3 pathway.

SIGNIFICANCE

JLX001 can alleviate MI/R injury by inhibiting myocardial apoptosis, inflammation, and oxidative stress via Jak2-Stat3 pathway in vivo and in vitro.

Small-molecule-mediated reprogramming: a silver lining for regenerative medicine

Techniques for reprogramming somatic cells create new opportunities for drug screening, disease modeling, artificial organ development, and cell therapy. The development of reprogramming techniques has grown exponentially since the discovery of induced pluripotent stem cells (iPSCs) by the transduction of four factors (OCT3/4, SOX2, c-MYC, and KLF4) in mouse embryonic fibroblasts. Initial studies on iPSCs led to direct-conversion techniques using transcription factors expressed mainly in target cells. However, reprogramming transcription factors with a virus risks integrating viral DNA and can be complicated by oncogenes. To address these problems, many researchers are developing reprogramming methods that use clinically applicable small molecules and growth factors. This review summarizes research trends in reprogramming cells using small molecules and growth factors, including their modes of action.

The reprogramming of cells using small molecules to generate viable, safe stem-cell populations could transform stem-cell therapies, disease modeling and artificial organ development. Existing ways of reprogramming cells to generate stem cells carry risks, because the methods used often involve using viral DNA components or oncogenes, genes with the potential to turn cells into tumour cells. Safer, inexpensive alternatives are sought by scientists, and the efficient reprogramming of cells using small molecules and growth factors shows promise. Dongho Choi and co-workers at Hanyang University College of Medicine in Seoul, South Korea, reviewed recent research highlighting how small molecules including chemical compounds, plant derivatives and certain approved drugs are being used effectively to create different stem-cell populations. Recent successes are also contributing valuable insights into how stem cells differentiate into different cell types.

Energy Metabolism in Cancer: The Roles of STAT3 and STAT5 in the Regulation of Metabolism-Related Genes

A central characteristic of many types of cancer is altered energy metabolism processes such as enhanced glucose uptake and glycolysis and decreased oxidative metabolism. The regulation of energy metabolism is an elaborate process involving regulatory proteins such as HIF (pro-metastatic protein), which reduces oxidative metabolism, and some other proteins such as tumour suppressors that promote oxidative phosphorylation. In recent years, it has been demonstrated that signal transducer and activator of transcription (STAT) proteins play a pivotal role in metabolism regulation. STAT3 and STAT5 are essential regulators of cytokine- or growth factor-induced cell survival and proliferation, as well as the crosstalk between STAT signalling and oxidative metabolism. Several reports suggest that the constitutive activation of STAT proteins promotes glycolysis through the transcriptional activation of hypoxia-inducible factors and therefore, the alteration of mitochondrial activity. It seems that STAT proteins function as an integrative centre for different growth and survival signals for energy and respiratory metabolism. This review summarises the functions of STAT3 and STAT5 in the regulation of some metabolism-related genes and the importance of oxygen in the tumour microenvironment to regulate cell metabolism, particularly in the metabolic pathways that are involved in energy production in cancer cells.

Drosophila muscles regulate the immune response against wasp infection via carbohydrate metabolism

We recently found that JAK/STAT signaling in skeletal muscles is important for the immune response of Drosophila larvae against wasp infection, but it was not clear how muscles could affect the immune response. Here we show that insulin signaling is required in muscles, but not in fat body or hemocytes, during larval development for an efficient encapsulation response and for the formation of lamellocytes. This effect requires TOR signaling. We show that muscle tissue affects the immune response by acting as a master regulator of carbohydrate metabolism in the infected animal, via JAK/STAT and insulin signaling in the muscles, and that there is indirect positive feedback between JAK/STAT and insulin signaling in the muscles. Specifically, stimulation of JAK/STAT signaling in the muscles can rescue the deficient immune response when insulin signaling is suppressed. Our results shed new light on the interaction between metabolism, immunity, and tissue communication.

IL-15 Activates the Jak3/STAT3 Signaling Pathway to Mediate Glucose Uptake in Skeletal Muscle Cells

Myokines are specialized cytokines that are secreted from skeletal muscle (SKM) in response to metabolic stimuli, such as exercise. Interleukin-15 (IL-15) is a myokine with potential to reduce obesity and increase lean mass through induction of metabolic processes. It has been previously shown that IL-15 acts to increase glucose uptake in SKM cells. However, the downstream signals orchestrating the link between IL-15 signaling and glucose uptake have not been fully explored. Here we employed the mouse SKM C2C12 cell line to examine potential downstream targets of IL-15-induced alterations in glucose uptake. Following differentiation, C2C12 cells were treated overnight with 100 ng/ml of IL-15. Activation of factors associated with glucose metabolism (Akt and AMPK) and known downstream targets of IL-15 (Jak1, Jak3, STAT3, and STAT5) were assessed with IL-15 stimulation. IL-15 stimulated glucose uptake and GLUT4 translocation to the plasma membrane. IL-15 treatment had no effect on phospho-Akt, phospho-Akt substrates, phospho-AMPK, phospho-Jak1, or phospho-STAT5. However, with IL-15, phospho-Jak3 and phospho-STAT3 levels were increased along with increased interaction of Jak3 and STAT3. Additionally, IL-15 induced a translocation of phospho-STAT3 from the cytoplasm to the nucleus. We have evidence that a mediator of glucose uptake, HIF1α, expression was dependent on IL-15 induced STAT3 activation. Finally, upon inhibition of STAT3 the positive effects of IL-15 on glucose uptake and GLUT4 translocation were abolished. Taken together, we provide evidence for a novel signaling pathway for IL-15 acting through Jak3/STAT3 to regulate glucose metabolism.

Cross-species gene expression analysis identifies a novel set of genes implicated in human insulin sensitivity

OBJECTIVE

Insulin resistance (IR) is one of the earliest predictors of type 2 diabetes. However, diagnosis of IR is limited. High fat fed mouse models provide key insights into IR. We hypothesized that early features of IR are associated with persistent changes in gene expression (GE) and endeavored to (a) develop novel methods for improving signal:noise in analysis of human GE using mouse models; (b) identify a GE motif that accurately diagnoses IR in humans; and (c) identify novel biology associated with IR in humans.

METHODS

We integrated human muscle GE data with longitudinal mouse GE data and developed an unbiased three-level cross-species analysis platform (single gene, gene set, and networks) to generate a gene expression motif (GEM) indicative of IR. A logistic regression classification model validated GEM in three independent human data sets (n=115).

RESULTS

This GEM of 93 genes substantially improved diagnosis of IR compared with routine clinical measures across multiple independent data sets. Individuals misclassified by GEM possessed other metabolic features raising the possibility that they represent a separate metabolic subclass. The GEM was enriched in pathways previously implicated in insulin action and revealed novel associations between β-catenin and Jak1 and IR. Functional analyses using small molecule inhibitors showed an important role for these proteins in insulin action.

CONCLUSIONS

This study shows that systems approaches for identifying molecular signatures provides a powerful way to stratify individuals into discrete metabolic groups. Moreover, we speculate that the β-catenin pathway may represent a novel biomarker for IR in humans that warrant future investigation.

Direct reprogramming of mouse fibroblasts into cardiomyocytes with chemical cocktails

The direct conversion, or transdifferentiation, of non-cardiac cells into cardiomyocytes by forced expression of transcription factors and microRNAs provides promising approaches for cardiac regeneration. However, genetic manipulations raise safety concerns and are thus not desirable in most clinical applications. The discovery of full chemically induced pluripotent stem cells suggest the possibility of replacing transcription factors with chemical cocktails. Here, we report the generation of automatically beating cardiomyocyte-like cells from mouse fibroblasts using only chemical cocktails. These chemical-induced cardiomyocyte-like cells (CiCMs) express cardiomyocyte-specific markers, exhibit sarcomeric organization, and possess typical cardiac calcium flux and electrophysiological features. Genetic lineage tracing confirms the fibroblast origin of these CiCMs. Further studies show the generation of CiCMs passes through a cardiac progenitor stage instead of a pluripotent stage. Bypassing the use of viral-derived factors, this proof of concept study lays a foundation for in vivo cardiac transdifferentiation with pharmacological agents and possibly safer treatment of heart failure.

Cardiopulmonary Bypass Decreases Activation of the Signal Transducer and Activator of Transcription 3 (STAT3) Pathway in Diabetic Human Myocardium

BACKGROUND

Cardiopulmonary bypass (CPB) is associated with increased myocardial oxidative stress and apoptosis in diabetic patients. A mechanistic understanding of this relationship could have therapeutic value. To establish a possible mechanism, we compared the activation of the cardioprotective signal transducer and activator of transcription 3 (STAT3) pathway between patients with uncontrolled diabetes (UD) and nondiabetic (ND) patients.

METHODS

Right atrial tissue and serum were collected before and after CPB from 80 patients, 39 ND and 41 UD (HbA1c ≥ 6.5), undergoing cardiac operations. The samples were evaluated with Western blotting, immunohistochemistry, and microarray.

RESULTS

On Western blot, leptin levels were significantly increased in ND post-CPB (p < 0.05). Compared with ND, the expression of Janus kinase 2 and phosphorylation (p-) of STAT3 was significantly decreased in UD (p < 0.05). The apoptotic proteins p-Bc12/Bc12 and caspase 3 were significantly increased (p < 0.05), antiapoptotic proteins Mcl-1, Bcl-2, and p-Akt were significantly decreased (p < 0.05) in UD compared with ND. The microarray data suggested significantly increased expression of interleukin-6 R, proapoptotic p-STAT1, caspase 9, and decreased expression of Bc12 and protein inhibitor of activated STAT1 antiapoptotic genes (p = 0.05) in the UD patients. The oxidative stress marker nuclear factor-κB was significantly higher (p < 0.05) in UD patients post-CPB compared with the pre-CPB value, but was decreased, albeit insignificantly, in ND patients post-CPB.

CONCLUSIONS

Compared with ND, UD myocardium demonstrated attenuation of the cardioprotective STAT3 pathway. Identification of this mechanism offers a possible target for therapeutic modulation.

Serine-727 phosphorylation activates hypothalamic STAT-3 independently from tyrosine-705 phosphorylation

Transcriptional activity of signal transducer and activator of transcription-3 (STAT-3) is a key element in the central regulation of appetite and energy homeostasis. Activation of hypothalamic STAT-3 has been attributed to cytokine-promoted phosphorylation at tyrosine-705 (Tyr-705). In nonhypothalamic cells, STAT-3 is also phosphorylated at serine-727 (Ser-727), but the functional significance of Ser-727 in the regulation of hypothalamic STAT-3 is not known. We used 2 hypothalamic cell lines and analyzed the effects of various hormones on STAT-3-dependent reporter gene activity and observed that IFN-γ, epidermal growth factor (EGF), and bradykinin (BK) induce similar STAT-3 reporter activation. EGF and BK solely increased Ser-727 and IFN-γ increased Tyr-705 phosphorylation of STAT-3. Specific inhibition of ERK-1/2 activity blocked EGF- and BK-induced STAT-3 activation and Ser-727 phosphorylation. BK-induced ERK-1/2 activation occurred via EGF receptor transactivation. Consequently, the BK-mediated effects on STAT-3 were blocked by a specific EGF receptor antagonist. Next, we analyzed the effects of IFN-γ and EGF on the expression of the STAT-3-dependent genes thyroliberin-releasing hormone and suppressors of cytokine signaling-3. EGF but not IFN-γ enhanced thyroliberin-releasing hormone expression via STAT-3. With regard to suppressors of cytokine signaling-3, we observed prolonged expression induced by IFN-γ and a transient effect of EGF that required coactivation of the activator protein-1. Thus, EGF-promoted Ser-727 phosphorylation by ERK-1/2 is not only sufficient to fully activate hypothalamic STAT-3, but, in terms of targeted genes and required cofactors, entails distinct modes of STAT-3 actions compared with IFN-γ-induced Tyr-705 phosphorylation.