AMP-activated protein kinase: a target for drugs both ancient and modern

Pharmacological Manipulation of Translation as a Therapeutic Target for Chronic Pain

Dysfunction in regulation of mRNA translation is an increasingly recognized characteristic of many diseases and disorders, including cancer, diabetes, autoimmunity, neurodegeneration, and chronic pain. Approximately 50 million adults in the United States experience chronic pain. This economic burden is greater than annual costs associated with heart disease, cancer, and diabetes combined. Treatment options for chronic pain are inadequately efficacious and riddled with adverse side effects. There is thus an urgent unmet need for novel approaches to treating chronic pain. Sensitization of neurons along the nociceptive pathway causes chronic pain states driving symptoms that include spontaneous pain and mechanical and thermal hypersensitivity. More than a decade of preclinical research demonstrates that translational mechanisms regulate the changes in gene expression that are required for ongoing sensitization of nociceptive sensory neurons. This review will describe how key translation regulation signaling pathways, including the integrated stress response, mammalian target of rapamycin, AMP-activated protein kinase (AMPK), and mitogen-activated protein kinase-interacting kinases, impact the translation of different subsets of mRNAs. We then place these mechanisms of translation regulation in the context of chronic pain states, evaluate currently available therapies, and examine the potential for developing novel drugs. Considering the large body of evidence now published in this area, we propose that pharmacologically manipulating specific aspects of the translational machinery may reverse key neuronal phenotypic changes causing different chronic pain conditions. Therapeutics targeting these pathways could eventually be first-line drugs used to treat chronic pain disorders. SIGNIFICANCE STATEMENT: Translational mechanisms regulating protein synthesis underlie phenotypic changes in the sensory nervous system that drive chronic pain states. This review highlights regulatory mechanisms that control translation initiation and how to exploit them in treating persistent pain conditions. We explore the role of mammalian/mechanistic target of rapamycin and mitogen-activated protein kinase-interacting kinase inhibitors and AMPK activators in alleviating pain hypersensitivity. Modulation of eukaryotic initiation factor 2α phosphorylation is also discussed as a potential therapy. Targeting specific translation regulation mechanisms may reverse changes in neuronal hyperexcitability associated with painful conditions.

RIPK1 Promotes Energy Sensing by the mTORC1 Pathway

The mechanisms of cellular energy sensing and AMPK-mediated mTORC1 inhibition are not fully delineated. Here, we discover that RIPK1 promotes mTORC1 inhibition during energetic stress. RIPK1 is involved in mediating the interaction between AMPK and TSC2 and facilitate TSC2 phosphorylation at Ser1387. RIPK1 loss results in a high basal mTORC1 activity that drives defective lysosomes in cells and mice, leading to accumulation of RIPK3 and CASP8 and sensitization to cell death. RIPK1-deficient cells are unable to cope with energetic stress and are vulnerable to low glucose levels and metformin. Inhibition of mTORC1 rescues the lysosomal defects and vulnerability to energetic stress and prolongs the survival of RIPK1-deficient neonatal mice. Thus, RIPK1 plays an important role in the cellular response to low energy levels and mediates AMPK-mTORC1 signaling. These findings shed light on the regulation of mTORC1 during energetic stress and unveil a point of crosstalk between pro-survival and pro-death pathways.

Metformin use reduced the risk of stomach cancer in diabetic patients in Korea: an analysis of Korean NHIS-HEALS database

BACKGROUND

Diabetes mellitus (DM) increases atherosclerotic cardiovascular complications and cancer risks. Stomach cancer is the most common cancer in Korea. Although the survival rate of stomach cancer has improved, the disease burden is still high.

METHODS

This retrospective study investigated the association between metformin use and stomach cancer incidence in a Korean population using the National Health Insurance Service-National Health Screening Cohort database. Participants aged 40-80 years old at the baseline period (2002-2003) were enrolled. The study population was categorized into three groups of metformin non-users with DM, metformin users with DM, and individuals without DM (No DM group).

RESULTS

A total of 347,895 participants (14,922 metformin non-users, 9891 metformin users, and 323,082 individuals without DM) were included in the final analysis. The median follow-up duration was 12.70 years. The estimated cumulative incidence of stomach cancer was highest in metformin non-users and lowest in the No DM group (men vs. women: 3.75 vs. 1.97% in metformin non-users, 2.91 vs. 1.53% in metformin users, and 2.54 vs. 0.95% in the No DM group). Compared with metformin non-users, the hazard ratios (95% confidence intervals) for stomach cancer incidence of metformin users and the No DM group were 0.710 (0.579-0.870) and 0.879 (0.767-1.006) in men and 0.700 (0.499-0.981) and 0.701 (0.544-0.903) in women, respectively, after full adjustment.

CONCLUSIONS

Metformin users with DM in the Korean population were at lower risk of stomach cancer incidence after controlling for potential confounding factors.

AMP-independent activator of AMPK for treatment of mitochondrial disorders

Mitochondrial diseases are a clinically heterogenous group of disorders caused by respiratory chain dysfunction and associated with progressive, multi-systemic phenotype. There is no effective treatment or cure, and no FDA-approved drug for treating mitochondrial disease. To identify and characterize potential therapeutic compounds, we developed an in vitro screening assay and identified a group of direct AMP-activated protein kinase (AMPK) activators originally developed for the treatment of diabetes and metabolic syndrome. Unlike previously investigated AMPK agonists such as AICAR, these compounds allosterically activate AMPK in an AMP-independent manner, thereby increasing specificity and decreasing pleiotropic effects. The direct AMPK activator PT1 significantly improved mitochondrial function in assays of cellular respiration, energy status, and cellular redox. PT1 also protected against retinal degeneration in a mouse model of photoreceptor degeneration associated with mitochondrial dysfunction and oxidative stress, further supporting the therapeutic potential of AMP-independent AMPK agonists in the treatment of mitochondrial disease.

Understanding the Biological Activities of Vitamin D in Type 1 Neurofibromatosis: New Insights into Disease Pathogenesis and Therapeutic Design

Vitamin D is a fat-soluble steroid hormone playing a pivotal role in calcium and phosphate homeostasis as well as in bone health. Vitamin D levels are not exclusively dependent on food intake. Indeed, the endogenous production-occurring in the skin and dependent on sun exposure-contributes to the majority amount of vitamin D present in the body. Since vitamin D receptors (VDRs) are ubiquitous and drive the expression of hundreds of genes, the interest in vitamin D has tremendously grown and its role in different diseases has been extensively studied. Several investigations indicated that vitamin D action extends far beyond bone health and calcium metabolism, showing broad effects on a variety of critical illnesses, including cancer, infections, cardiovascular and autoimmune diseases. Epidemiological studies indicated that low circulating vitamin D levels inversely correlate with cutaneous manifestations and bone abnormalities, clinical hallmarks of neurofibromatosis type 1 (NF1). NF1 is an autosomal dominant tumour predisposition syndrome causing significant pain and morbidity, for which limited treatment options are available. In this context, vitamin D or its analogues have been used to treat both skin and bone lesions in NF1 patients, alone or combined with other therapeutic agents. Here we provide an overview of vitamin D, its characteristic nutritional properties relevant for health benefits and its role in NF1 disorder. We focus on preclinical and clinical studies that demonstrated the clinical correlation between vitamin D status and NF1 disease, thus providing important insights into disease pathogenesis and new opportunities for targeted therapy.

Hotspot Analysis of Traditional Drugs in Diabetes Treatment Literature

OBJECTIVE

To summarize current hotspots and predict the potential trends in traditional drugs of diabetes treatment for further research.

METHODS

Publications on the application of traditional drugs in diabetes treatment were searched from PubMed without language limits. Highly frequent MeSH terms were identified through Bibliographic Item Co-Occurrence Matrix Builder (BICOMB). Biclustering analysis results were visualized utilizing the gCLUTO software. Finally, a strategic diagram was generated.

RESULTS

Totally 2,386 relevant publications were obtained from PubMed on November 9th, 2018, and 69 highly frequent MeSH terms were identified. Biclustering analysis revealed that these highly frequent MeSH terms were classified into 7 clusters. After calculating the density and centrality of each cluster, strategy diagram was presented. Cluster 0 "Chinese medicine monomers such as antioxidant and hypoglycemic effects" was considered as the most potential research hotspot.

CONCLUSIONS

In this study, we found 7 topics related to the application of traditional drugs in diabetes treatment. The molecular mechanisms of Chinese medicine monomers in diabetes could become a potential hotspot with high centricity and low density.

Effects of aspirin on the gastrointestinal tract: Pros vs. cons

Acetylsalicylic acid, also known as aspirin, is often used in clinical antipyretic, analgesic and antiplatelet therapy. Aspirin can cause numerous side effects in the gastrointestinal (GI) tract, ranging from unpleasant GI symptoms without gastric mucosal lesions to ulcer bleeding and even death. However, recent studies have found that aspirin can significantly prevent GI tumors. Despite impressive advances in cancer research, screening and treatment options, GI tumors remain a leading cause of death worldwide. Prevention is a far better option than treatment for tumors. Therefore, the present review assesses the pros and cons of aspirin on the GI tract and, on this the basis, the appropriate dose of aspirin to protect it.

AMPK, Mitochondrial Function, and Cardiovascular Disease

Adenosine monophosphate-activated protein kinase (AMPK) is in charge of numerous catabolic and anabolic signaling pathways to sustain appropriate intracellular adenosine triphosphate levels in response to energetic and/or cellular stress. In addition to its conventional roles as an intracellular energy switch or fuel gauge, emerging research has shown that AMPK is also a redox sensor and modulator, playing pivotal roles in maintaining cardiovascular processes and inhibiting disease progression. Pharmacological reagents, including statins, metformin, berberine, polyphenol, and resveratrol, all of which are widely used therapeutics for cardiovascular disorders, appear to deliver their protective/therapeutic effects partially via AMPK signaling modulation. The functions of AMPK during health and disease are far from clear. Accumulating studies have demonstrated crosstalk between AMPK and mitochondria, such as AMPK regulation of mitochondrial homeostasis and mitochondrial dysfunction causing abnormal AMPK activity. In this review, we begin with the description of AMPK structure and regulation, and then focus on the recent advances toward understanding how mitochondrial dysfunction controls AMPK and how AMPK, as a central mediator of the cellular response to energetic stress, maintains mitochondrial homeostasis. Finally, we systemically review how dysfunctional AMPK contributes to the initiation and progression of cardiovascular diseases via the impact on mitochondrial function.

Probiotic Bifidobacterium lactis V9 attenuates hepatic steatosis and inflammation in rats with non-alcoholic fatty liver disease

Both steatosis and inflammation are key pathological events in the progression of non-alcoholic fatty liver disease (NAFLD). Probiotics are beneficial for the prevention and treatment of NAFLD. Bifidobacterium animalis subsp. lactis V9 (V9) is a newly isolated strain with favorable probiotic properties. The study aims to evaluate the effects and mechanisms of V9 on the hepatic steatosis and inflammatory responses in a rat model of NAFLD induced by high-fat diets (HFD). Our results showed that administration of V9 significantly attenuated the HFD-induced increases in alanine transaminase (ALT) and aspartate aminotransferase (AST) levels, resulting in alleviated hepatic steatosis. V9 supplementation reduced the accumulation of hepatic triglyceride and free fatty acid,while increasing the levels of glycogen. Serum levels of glucose were also decreased in HFD rats administrated with V9. Meanwhile, the transcription of SREBP-1c and FAS was reduced, and the hepatic expression of phosphorylated-AMPK and PPAR-α was restored after V9 administration. V9 suppressed the production of inflammatory cytokines (e.g. IL-6, IL-1β, and TNF-α) in HFD-fed rats. The anti-inflammatory effects of V9 was found to be associated with the inhibition of hepatic expression of TLR4, TLR9, NLRP3, and ASC mRNA. Furthermore, the activation of ERK, JNK, AKT and NF-κB were suppressed by V9 treatment. These results indicate that Bifidobacterium lactis V9 improves NAFLD by regulating de novo lipid synthesis and suppressing inflammation through AMPK and TLR-NF-κB pathways, respectively.

Targeting PI3K and AMPKα Signaling Alone or in Combination to Enhance Radiosensitivity of Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) is the most aggressive breast cancer subtype and is characterized by poor survival. Radiotherapy plays an important role in treating TNBC. The purpose of this study was to determine whether inhibiting the AMP-activated protein kinase (AMPK) and phosphatidylinositol 3-kinase (PI3K) pathways alone or in combination potentiates radiotherapy in TNBC. AMPKα1 and AMPKα2 knockdown diminished cyclin D1 expression and induced G1 cell cycle arrest but did not induce apoptosis alone or in combination with radiotherapy. Next, we analyzed the role of PI3K p85α, p85β, p110α, p110β, Akt1, and Akt2 proteins on TNBC cell cycle progression and apoptosis induction. Akt1 and p110α knockdown diminished cyclin D1 expression and induced apoptosis. Silencing Akt1 promoted synergistic apoptosis induction during radiotherapy and further reduced survival after radiation. Treatment with the Akt inhibitor, MK-2206 48 h after radiotherapy decreased Akt1 levels and potentiated radiation-induced apoptosis. Together, our results demonstrate that AMPKα, p110α, and Akt1 promote TNBC proliferation and that Akt1 is a key regulator of radiosensitivity in TNBC. Importantly, combining radiotherapy with the pharmacological inhibition of Akt1 expression is a potentially promising approach for the treatment of TNBC.

Metformin arrests the progression of established kidney disease in the subtotal nephrectomy model of chronic kidney disease

Metformin, an AMP-activated protein kinase (AMPK) activator, has been shown in previous studies to reduce kidney fibrosis in different models of experimental chronic kidney disease (CKD). However, in all of these studies, the administration of metformin was initiated before the establishment of renal disease, which is a condition that does not typically occur in clinical settings. The aim of the present study was to investigate whether the administration of metformin could arrest the progression of established renal disease in a well-recognized model of CKD, the subtotal kidney nephrectomy (Nx) model. Adult male Munich-Wistar rats underwent either Nx or sham operations. After the surgery (30 days), Nx rats that had systolic blood pressures of >170 mmHg and albuminuria levels of >40 mg/24 h were randomized to a no-treatment condition or to a treatment condition with metformin (300 mg·kg−1·day−1) for a period of either 60 or 120 days. After 60 days of treatment, we did not observe any differences in kidney disease parameters between Nx metformin-treated and untreated rats. However, after 120 days, Nx rats that had been treated with metformin displayed significant reductions in albuminuria levels and in markers of renal fibrosis. These effects were independent of any other effects on blood pressure or glycemia. In addition, treatment with metformin was also able to activate kidney AMPK and therefore improve mitochondrial biogenesis. It was concluded that metformin can arrest the progression of established kidney disease in the Nx model, likely via the activation of AMPK.

Redox Homeostasis and Metabolism in Cancer: A Complex Mechanism and Potential Targeted Therapeutics

Reactive Oxygen Species or "ROS" encompass several molecules derived from oxygen that can oxidize other molecules and subsequently transition rapidly between species. The key roles of ROS in biological processes are cell signaling, biosynthetic processes, and host defense. In cancer cells, increased ROS production and oxidative stress are instigated by carcinogens, oncogenic mutations, and importantly, metabolic reprograming of the rapidly proliferating cancer cells. Increased ROS production activates myriad downstream survival pathways that further cancer progression and metastasis. In this review, we highlight the relation between ROS, the metabolic programing of cancer, and stromal and immune cells with emphasis on and the transcription machinery involved in redox homeostasis, metabolic programing and malignant phenotype. We also shed light on the therapeutic targeting of metabolic pathways generating ROS as we investigate: Orlistat, Biguandes, AICAR, 2 Deoxyglucose, CPI-613, and Etomoxir.

MSCs ameliorate hepatocellular apoptosis mediated by PINK1-dependent mitophagy in liver ischemia/reperfusion injury through AMPKα activation

Hepatocyte apoptosis is the main pathophysiological process underlying liver ischemia/reperfusion (I/R) injury. Mitochondrial abnormalities have a vital role in hepatocellular damage. The hepatoprotective effects of mesenchymal stem cells (MSCs) have been previously demonstrated. In this study, we aim to investigate the effect and potential mechanism of MSCs against liver I/R injury. Effects of MSCs were studied in mice liver I/R injury model and in a hypoxia/reoxygenation (H/R) model of L02 hepatocytes. The potential mechanisms of MSCs on these in vivo and in vitro I/R-induced hepatocellular apoptosis models were studies. Accompanied by the improvement of hepatic damage, MSCs exhibited capabilities of controlling mitochondrial quality, shown by reduced mitochondrial reactive oxygen species (mtROS) overproduction, decreased the accumulation of mitochondrial fragmentation, restored ATP generation and upregulated mitophagy. Furthermore, we descripted a potential mechanism of MSCs on upregulating mitophagy and found that the reduced Parkin and PINK1 expression and inactivated AMPKα pathway were observed in the liver tissue in I/R model. These effects were reversed by MSCs treatment. In vitro study showed that MSC-conditioned medium (MSC-CM) suppressed hepatocellular apoptosis and inhibited mtROS accumulation in the H/R environment. And these effects of MSC-CM were partially blocked after the cells were transfected with PINK1 siRNA or added with dorsomorphin. Collectively, our findings provide a novel pharmacological mechanism that MSCs exert hepatoprotective effect in liver I/R injury via upregulating PINK1-dependent mitophagy. In addition, this effect might be attributed to the modulation of AMPKα activation.

ZEA-induced autophagy in TM4 cells was mediated by the release of Ca2+ activates CaMKKβ-AMPK signaling pathway in the endoplasmic reticulum

Zearalenone (ZEA) is a prevalent non-steroidal estrogenic mycotoxin produced mainly by Fusarium contamination. Our previous study showed that ZEA induces the autophagy of Sertoli cells (SCs). However, the underlying mechanisms are still unknown. Several studies have indicated that the increasing level of cytoplasmic Ca²⁺ could induce autophagy through CaMKKβ and AMPK pathways. Thus in order to investigate the potential mechanism underlying ZEA-induced autophagy, the activity of calmodulin-dependent kinase kinase β(CaMKKβ)and AMP-activated protein kinase (AMPK) signaling pathway in ZEA-infected TM4 cells was studied. In the present study, ZEA activated the CaMKKβ and AMPK signaling pathways. The AMPK inhibitor and activator significantly inhibited and stimulated the effect of ZEA on AMPK, the transformation from LC3I to LC3II, and the distribution of LC3 dots. In addition, cytosolic calcium (Ca²⁺) was increased gradually with the concentration of ZEA. After treatment of ZEA-infected cells with 1, 2-bis (2-aminophenoxy) ethane-N, N, N', N'- tetraacetic acid- tetraac etoxymethyl ester (BAPTA-AM) and 2-aminoethyl diphenylborinate (2-APB), the intracellular concentration of Ca²⁺ reduced significantly. Also, the activities of CaMKKβ and AMPK and subsequent autophagy decreased. Moreover, the antioxidant NAC significantly decreased activities of AMPK and autophagy -related protein. Therefore, it can be speculated that ROS- mediated ER-stress induced by ZEA activates AMPK via Ca²⁺-CaMKKβ leading to autophagy in TM4 cells.

T cell metabolism in graft-versus-host disease

Graft-versus-host disease (GVHD) is a major source of morbidity and mortality following allogeneic hematopoietic stem cell transplant (allo-HSCT), one of the most effective approaches to treat hematopoietic malignancies.¹ However, current prophylaxis regimens and treatments that reduce the detrimental effect of acute GVHD can be offset by increased incidence in opportunistic infections and relapse of the primary malignancy.² In addition, the majority of the approaches that inhibit T cell responses are non-specific, resulting in the inhibition of both alloreactive T cells and protective T cells from the donor. Therefore, there is an increase in the demand to develop novel approaches that selectively target alloreactive T cells. One potential means to address this issue is to take advantage of the unique metabolic profile of activated T cells.

Compound 13 activates AMPK-Nrf2 signaling to protect neuronal cells from oxygen glucose deprivation-reoxygenation

Oxygen glucose deprivation-reoxygenation (OGD-R) causes the production of reactive oxygen species (ROS) and oxidative injury in neuronal cells. We tested the potential neuroprotective function of compound 13 (C13), a novel AMP-activated protein kinase (AMPK) activator, against OGD-R. We show that C13 pretreatment protected SH-SY5Y neuronal cells and primary hippocampal neurons from OGD-R. C13 activated AMPK signaling in SH-SY5Y cells and primary neurons. It significantly inhibited OGD-R-induced apoptosis activation in neuronal cells. Conversely, AMPKα1 shRNA or knockout reversed C13-mediated neuroprotection against OGD-R. C13 potently inhibited OGD-R-induced ROS production and oxidative stress in SH-SY5Y cells and primary neurons. Furthermore, C13 induced Keap1 downregulation and Nrf2 activation, causing Nrf2 stabilization, nuclear accumulation, and expression of Nrf2-dependent genes. Nrf2 silencing or knockout in SH-SY5Y cells abolished C13-mediated neuroprotection against OGD-R. In conclusion, C13 activates AMPK-Nrf2 signaling to protect neuronal cells from OGD-R.

Ezetimibe ameliorates lipid accumulation during adipogenesis by regulating the AMPK-mTORC1 pathway

Adipogenesis, a critical process that converts adipocyte precursors into adipocytes, is considered a potential therapeutic target for the treatment of obesity. Ezetimibe, a drug approved by the United States Food and Drug Administration, is used for the treatment of hypercholesterolemia. Recently, it was reported to ameliorate high fat diet-induced dyslipidemia in mice and reduce lipid accumulation in hepatocytes through the activation of AMPK. However, the anti-adipogenic effects of ezetimibe and the underlying molecular mechanism have not yet been elucidated. Here, we found that ezetimibe reduced lipid accumulation via activating AMPK during the early phase of adipogenesis. We also observed that ezetimibe inhibited peroxisome proliferator-activated receptor γ, which is a major transcription factor of adipogenesis. Furthermore, ezetimibe-mediated AMPK activation reduced lipid accumulation by inhibiting mTORC1 signaling, leading to the downregulation of lipogenesis-related genes. Mitotic clonal expansion, required for adipogenesis, accelerates cell cycle progression and cell proliferation. We additionally observed that ezetimibe prevented the progression of mitotic clonal expansion by arresting the cell cycle at the G0/G1 phase, which was followed by the inhibition of cell proliferation. Collectively, ezetimibe-mediated inhibition of adipogenesis is dependent on the AMPK-mTORC1 pathway. Thus, we suggest that ezetimibe might be a promising drug for the treatment of obesity.

Inonotus obliquus polysaccharides induces apoptosis of lung cancer cells and alters energy metabolism via the LKB1/AMPK axis

The present study explores the mechanisms underlying the anti-cancer action of Inonotus obliquus polysaccharides (IOP). Thus, we characterized the IOP components extracted from Chaga sclerotium and, found that the extracts contained 70% polysaccharides with an average molecular weight of 4.5 × 10⁴ Da consisting of 75% glucose. We then showed that IOP extract activated AMPK in lung cancer cells expressing LKB1, suppressed cell viability, colony-formation, and triggered cell apoptosis. In conjunction, IOP downregulated Bcl-2, upregulated Bax, and enhanced cleavage of Caspase-3 and PARP. All of these effects were prevented by treatment with Compound C, a chemical inhibitor of AMPK. IOP diminished mitochondrial membrane potential (MMP), concurrent with decreases in oxidative phosphorylation and glycolysis, which was dependent on LKB1/AMPK. Finally, IOP at a dosage of 50 mg/kg significantly inhibited allograft tumor growth of the LLC1 cells in association with increased apoptosis. Collectively, our results demonstrate that IOP acts on cancer cells through a mechanism by which AMPK triggers the apoptotic pathway via the opening of mitochondrial permeability transition pore, and reducing MMP, leading to an inhibition of ATP production. Therefore, our study provides a solid foundation for the use of IOP as a promising alternative or supplementary medicine for cancer therapy.

Knockout model reveals the role of Nischarin in mammary gland development, breast tumorigenesis and response to metformin treatment

Previously, our lab discovered the protein Nischarin and uncovered its role in regulating cell migration and invasion via its interactions with several proteins. We subsequently described a role for Nischarin in breast cancer, in which it is frequently underexpressed. To characterize Nischarin's role in breast tumorigenesis and mammary gland development more completely, we deleted a critical region of the Nisch gene (exons 7-10) from the mouse genome and observed the effects. Mammary glands in mutant animals showed delayed terminal end bud formation but did not develop breast tumors spontaneously. Therefore, we interbred the animals with transgenic mice expressing the mouse mammary tumor virus-polyoma middle T-antigen (MMTV-PyMT) oncogene. The MMTV-PyMT mammary glands lacking Nischarin showed increased hyperplasia compared to wild-type animal tissues. Furthermore, we observed significantly increased tumor growth and metastasis in Nischarin mutant animals. Surprisingly, Nischarin deletion decreased activity of AMPK and subsequently its downstream effectors. Given this finding, we treated these animals with metformin, which enhances AMPK activity. Here, we show for the first time, metformin activates AMPK signaling and inhibits tumor growth of Nischarin lacking PyMT tumors suggesting a potential use for metformin as a cancer therapeutic, particularly in the case of Nischarin-deficient breast cancers.

LKB1/AMPK Pathway and Drug Response in Cancer: A Therapeutic Perspective

Inactivating mutations of the tumor suppressor gene Liver Kinase B1 (LKB1) are frequently detected in non-small-cell lung cancer (NSCLC) and cervical carcinoma. Moreover, LKB1 expression is epigenetically regulated in several tumor types. LKB1 has an established function in the control of cell metabolism and oxidative stress. Clinical and preclinical studies support a role of LKB1 as a central modifier of cellular response to different stress-inducing drugs, suggesting LKB1 pathway as a highly promising therapeutic target. Loss of LKB1-AMPK signaling confers sensitivity to energy depletion and to redox homeostasis impairment and has been associated with an improved outcome in advanced NSCLC patients treated with chemotherapy. In this review, we provide an overview of the interplay between LKB1 and its downstream targets in cancer and focus on potential therapeutic strategies whose outcome could depend from LKB1.

AMPK Activation Promotes Tight Junction Assembly in Intestinal Epithelial Caco-2 Cells

The AMP-activated protein kinase (AMPK) is principally known as a major regulator of cellular energy status, but it has been recently shown to play a key structural role in cell-cell junctions. The aim of this study was to evaluate the impact of AMPK activation on the reassembly of tight junctions in intestinal epithelial Caco-2 cells. We generated Caco-2 cells invalidated for AMPK α1/α2 (AMPK dKO) by CRISPR/Cas9 technology and evaluated the effect of the direct AMPK activator 991 on the reassembly of tight junctions following a calcium switch assay. We analyzed the integrity of the epithelial barrier by measuring the trans-epithelial electrical resistance (TEER), the paracellular permeability, and quantification of zonula occludens 1 (ZO-1) deposit at plasma membrane by immunofluorescence. Here, we demonstrated that AMPK deletion induced a delay in tight junction reassembly and relocalization at the plasma membrane during calcium switch, leading to impairments in the establishment of TEER and paracellular permeability. We also showed that 991-induced AMPK activation accelerated the reassembly and reorganization of tight junctions, improved the development of TEER and paracellular permeability after calcium switch. Thus, our results show that AMPK activation ensures a better recovery of epithelial barrier function following injury.

Hepatic Transcriptomics Reveals that Lipogenesis Is a Key Signaling Pathway in Isocitrate Dehydrogenase 2 Deficient Mice

Mitochondrial nicotinamide adenine dinucleotide phosphate (NADP⁺)-dependent isocitrate dehydrogenase (IDH2) plays a key role in the intermediary metabolism and energy production via catalysing oxidative decarboxylation of isocitrate to α-ketoglutarate in the tricarboxylic acid (TCA) cycle. Despite studies reporting potential interlinks between IDH2 and various diseases, there is lack of effort to comprehensively characterize signature(s) of IDH2 knockout (IDH2 KO) mice. A total of 6583 transcripts were identified from both wild-type (WT) and IDH2 KO mice liver tissues. Afterwards, 167 differentially expressed genes in the IDH2 KO group were short-listed compared to the WT group based on our criteria. The online bioinformatic analyses indicated that lipid metabolism is the most significantly influenced metabolic process in IDH2 KO mice. Moreover, the TR/RXR activation pathway was predicted as the top canonical pathway significantly affected by IDH2 KO. The key transcripts found in the bioinformatic analyses were validated by qPCR analysis, corresponding to the transcriptomics results. Further, an additional qPCR analysis confirmed that IDH2 KO caused a decrease in hepatic de novo lipogenesis via the activation of the fatty acid β-oxidation process. Our unbiased transcriptomics approach and validation experiments suggested that IDH2 might play a key role in homeostasis of lipid metabolism.

Comparative analysis of stimulation and binding characteristics of adenosine analogs to AMP-activated protein kinase

To compare the stimulation and binding characteristics of adenosine analogs including AMP, IMM-H007, and M1, to AMPK, and to explore the potential mechanism underlying the regulation effect of adenosine analogs on AMPK activity, [γ-³²P]ATP assay, circular dichroism experiments and molecular docking test were performed. We found that the interactions with Thr86, Thr88, and His150 in site 1 are probably the reason why the affinities of IMM-H007, M1, and adenosine are comparable but their allosteric activation on AMPK varies greatly, partly interpreting the mechanism of AMPK activity regulated by adenosine analogs.

Metabolism and mitochondria in polycystic kidney disease research and therapy

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common, potentially lethal, monogenic diseases and is caused predominantly by mutations in polycystic kidney disease 1 (PKD1) and PKD2, which encode polycystin 1 (PC1) and PC2, respectively. Over the decades-long course of the disease, patients develop large fluid-filled renal cysts that impair kidney function, leading to end-stage renal disease in ~50% of patients. Despite the identification of numerous dysregulated pathways in ADPKD, the molecular mechanisms underlying the renal dysfunction from mutations in PKD genes and the physiological functions of the polycystin proteins are still unclear. Alterations in cell metabolism have emerged in the past decade as a hallmark of ADPKD. ADPKD cells shift their mode of energy production from oxidative phosphorylation to alternative pathways, such as glycolysis. In addition, the polycystins seem to play regulatory roles in modulating mechanisms and machinery related to energy production and utilization, including AMPK, PPARα, PGC1α, calcium signalling at mitochondria-associated membranes, mTORC1, cAMP and CFTR-mediated ion transport as well as the expression of crucial components of the mitochondrial energy production apparatus. In this Review, we explore these metabolic changes and discuss in detail the relationship between energy metabolism and ADPKD pathogenesis and identify potential therapeutic targets.

Activation of AMPK by Medicinal Plants and Natural Products: Its Role in Type 2 Diabetes Mellitus

Type-2 Diabetes (T2D) is a metabolic disease characterized by permanent hyperglycemia, whose development can be prevented or delayed by using therapeutic agents and implementing lifestyle changes. Some therapeutic alternatives include regulation of glycemia through modulation of different mediators and enzymes, such as AMP-activated protein kinase (AMPK), a highly relevant cellular energy sensor for metabolic homeostasis regulation, with particular relevance in the modulation of liver and muscle insulin sensitivity. This makes it a potential therapeutic target for antidiabetic drugs. In fact, some of them are standard drugs used for treatment of T2D, such as biguanides and thiazolidindiones. In this review, we compile the principal natural products that are activators of AMPK and their effect on glucose metabolism, which could make them candidates as future antidiabetic agents. Phenolics such as flavonoids and resveratrol, alkaloids such as berberine, and some saponins are potential natural activators of AMPK with a potential future as antidiabetic drugs.

CircACC1 Regulates Assembly and Activation of AMPK Complex under Metabolic Stress

We report that circACC1, a circular RNA derived from human ACC1, plays a critical role in cellular responses to metabolic stress. CircACC1 is preferentially produced over ACC1 in response to serum deprivation by the transcription factor c-Jun. It functions to stabilize and promote the enzymatic activity of the AMPK holoenzyme by forming a ternary complex with the regulatory β and γ subunits. The cellular levels of circACC1 modulate both fatty acid β-oxidation and glycolysis, resulting in profound changes in cellular lipid storage. In a tumor xenograft model, silencing or enforced expression of circACC1 resulted in growth inhibition and enhancement, respectively. Moreover, increased AMPK activation in colorectal cancer tissues was frequently associated with elevated circACC1 expression. We conclude that circACC1 serves as an economic means to elicit AMPK activation and moreover propose that cancer cells exploit circACC1 during metabolic reprogramming.

Lipid Metabolism as a Source of Druggable Targets for Antiviral Discovery against Zika and Other Flaviviruses

The Zika virus (ZIKV) is a mosquito-borne flavivirus that can lead to birth defects (microcephaly), ocular lesions and neurological disorders (Guillain-Barré syndrome). There is no licensed vaccine or antiviral treatment against ZIKV infection. The effort to understand the complex interactions of ZIKV with cellular networks contributes to the identification of novel host-directed antiviral (HDA) candidates. Among the cellular pathways involved in infection, lipid metabolism gains attention. In ZIKV-infected cells lipid metabolism attributed to intracellular membrane remodeling, virion morphogenesis, autophagy modulation, innate immunity and inflammation. The key roles played by the cellular structures associated with lipid metabolism, such as peroxisomes and lipid droplets, are starting to be deciphered. Consequently, there is a wide variety of lipid-related antiviral strategies that are currently under consideration, which include an inhibition of sterol regulatory element-binding proteins (SREBP), the activation of adenosine-monophosphate activated kinase (AMPK), an inhibition of acetyl-Coenzyme A carboxylase (ACC), interference with sphingolipid metabolism, blockage of intracellular cholesterol trafficking, or a treatment with cholesterol derivatives. Remarkably, most of the HDAs identified in these studies are also effective against flaviviruses other than ZIKV (West Nile virus and dengue virus), supporting their broad-spectrum effect. Considering that lipid metabolism is one of the main cellular pathways suitable for pharmacological intervention, the idea of repositioning drugs targeting lipid metabolism as antiviral candidates is gaining force.

Combination simvastatin and metformin synergistically inhibits endometrial cancer cell growth

OBJECTIVE

Recent data show that simvastatin (SIM) and metformin (MET) have anti-proliferative effects in endometrial cancer cells. The combination (MET+SIM) inhibits tumor growth and metastasis in prostate cancer cells which possess similar molecular alterations to many early endometrial cancers. We tested the hypothesis that the anti-proliferative effects of MET+SIM in endometrial cancer cells would be greater than the effects of each agent alone.

METHODS

RL95-2, HEC1B, and Ishikawa endometrial cancer cell lines were treated with MET and/or SIM. Growth inhibition was measured by MTS cell proliferation assays. Apoptosis was evaluated by caspase-3, Annexin V, and TUNEL assays and by apoptosis markers (BAX, Bcl-2, Bim) using western blot. Bim was silenced using Bim siRNA to confirm this apoptotic pathway. Treatment effects on the mTOR pathway were investigated by western blot using antibodies to phosphorylated (phospho)-AMPK and phospho-S6.

RESULTS

MET+SIM synergistically inhibited growth in all three cell lines. The combination induced apoptosis as measured by TUNEL, Annexin V, and caspase-3 assays. Bim siRNA transfection abrogated this effect-silencing Bim in MET+SIM-treated RL95-2 cells rescued cell viability in MTS assays and reduced caspase-3 activity compared with control siRNA-transfected cells. Combination treatment upregulated phosphorylated AMPK and downregulated downstream phosphorylated S6, suggesting mTOR inhibition as a mechanism for these anti-proliferative effects.

CONCLUSIONS

MET+SIM treatment synergistically inhibits endometrial cancer cell viability. This may be mediated by apoptosis and mTOR pathway inhibition. Our results provide preclinical evidence that the combination of these well-tolerated drugs may warrant further clinical investigation for endometrial cancer treatment.

Expression of messenger RNA encoding two cellular metabolic regulators, AMP-activated protein kinase (AMPK) and O-GlcNAc transferase (OGT), in channel catfish: Their tissue distribution and relationship with changes in food intake

AMP-activated protein kinase (AMPK) is considered as the master cellular metabolism regulator that activates various proteins, including O-GlcNAc transferase (OGT). Physiological roles of AMPK and OGT, including the relationship between their mRNA expression and food intake, are poorly understood in channel catfish. This study examined the tissue distribution of AMPK and OGT mRNA and changes in their expression in response to changes in food intake in channel catfish. Expression of all AMPK subunit and OGT mRNA was detectable in the whole brain, liver, heart, spleen, white muscle, and kidney of channel catfish. The OGT mRNA was highly localized in the brain compared to other tissues. 28-day fasting increased hepatic expression of AMPK α1, β1, and OGT mRNA while refeeding fish for 14 days after the 14-day fast decreased their expression to the level similar to that of fish that were fed daily. No changes were noted in the expression of muscle and brain AMPK mRNA or OGT mRNA by fasting and refeeding. Hepatic AMPK α1, α2 and β1 mRNA decreased in response to increased feeding frequency, whereas no changes in the expression of AMPK or OGT mRNA were noted in the brain or the muscle. Results of the current study indicated that the hepatic expression of AMPK and OGT mRNA appeared to be more sensitive to changes in food intake in channel catfish. However, further studies are needed to clearly demonstrate if food intake influences the expression of AMPK and OGT mRNA in various tissues, including the hypothalamus.

A novel traditional Chinese medicine ameliorates fatigue-induced cardiac hypertrophy and dysfunction via regulation of energy metabolism

Prolonged exercise and exercise training can adversely affect cardiac function in some individuals. QiShenYiQi Pills (QSYQ), which are a compound Chinese medicine, have been previously shown to improve pressure overload-induced cardiac hypertrophy. We hypothesized that QSYQ can ameliorate as well the fatigue-induced cardiac hypertrophy. This study was to test this hypothesis and underlying mechanism with a focus on its role in energy regulation. Male Sprague-Dawley rats were used to establish exercise adaptation and fatigue model on a motorized rodent treadmill. Echocardiographic analysis and heart function test were performed to assess heart systolic function. Food-intake weight/body weight and heart weight/body weight were assessed, and hematoxylin and eosin staining and immunofluorescence staining of myocardium sections were performed. ATP synthase expression and activity and ATP, ADP, and AMP levels were assessed using Western blot and ELISA. Expression of proteins related to energy metabolism and IGF-1R signaling was determined using Western blot. QSYQ attenuated the food-intake weight/body weight decrease, improved myocardial structure and heart function, and restored the expression and distribution of myocardial connexin 43 after fatigue, concomitant with an increased ATP production and a restoration of metabolism-related protein expression. QSYQ upgraded the expression of IGF-1R, P-AMPK/AMPK, peroxisome proliferator-activated receptor-γ coactivator-1α, nuclear respiratory factor-1, P-phosphatidylinositol 3-kinase (PI3K)/PI3K, and P-Akt/Akt thereby attenuated the dysregulation of IGF-1R signaling after fatigue. QSYQ relieved fatigue-induced cardiac hypertrophy and enhanced heart function, which is correlated with its potential to improve energy metabolism by regulating IGF-1R signaling. NEW & NOTEWORTHY Prolonged exercise may impact some people leading to pathological cardiac hypertrophy. This study using an animal model of fatigue-induced cardiac hypertrophy provides evidence showing the potential of QiShenYiQi Pills, a novel traditional Chinese medicine, to prevent the cardiac adaptive hypertrophy from development to pathological hypertrophy and demonstrates that this effect is correlated with its capacity for regulating energy metabolism through interacting with insulin-like growth factor-1 receptor.

Silence of long non-coding RNA UCA1 inhibits hemangioma cells growth, migration and invasion by up-regulation of miR-200c

BACKGROUND

Human urothelial carcinoma associated 1 (UCA1) has been recognized as an oncogenic lncRNA in various cancers, except infantile hemangioma (IH). This study attempts to explore the functional role of lncRNA UCA1 in IH.

METHODS

qRT-PCR was carried out to detect the expression of lncRNA UCA1 in human IH tissues. Two hemangioma cell lines (EOMA and HemECs) were transfected with shRNAs specific for lncRNA UCA1, or a plasmid for expression lncRNA UCA1. The expression of miR-200c in cell was suppressed or overexpressed by miRNA-mediated transfection. CCK-8 assay, flow cytometry, Transwell assay, and Western blot were performed to detect cell survival, migration and invasion.

RESULTS

LncRNA UCA1 was up-regulated in proliferating-phase hemangioma samples, as compared to involuting-phase. Silence of lncRNA UCA1 significantly reduced EOMA cells viability, migration and invasion, and induced apoptosis. These observations were coupled with the down-regulations of CyclinD1, CDK6 and CDK4, the cleavage of caspase-3 and caspase-9, as well as the decreased expression levels of MMP-9 and Vimentin. miR-200c was highly expressed in lncRNA UCA1 silenced-cells. Besides, the anti-tumor effects of lncRNA UCA1 silence towards EOMA cells were reversed by miR-200c suppression. Same effects of lncRNA UCA1 and miR-200c on HemECs cells were observed. Furthermore, silence of lncRNA UCA1 repressed mTOR, AMPK and Wnt/β-catenin signaling via a miR-200c-dependent fashion.

CONCLUSION

This study evidences that silence of lncRNA UCA1 inhibits hemangioma cells growth, migration and invasion possibly via its regulation on miR-200c expression and the activation of mTOR, AMPK and Wnt/β-catenin signaling pathways.

Induction of AMPK activation by N,N'-diarylurea FND-4b decreases growth and increases apoptosis in triple negative and estrogen-receptor positive breast cancers

Purpose

Triple negative breast cancer (TNBC) is the most lethal and aggressive subtype of breast cancer. AMP-activated protein kinase (AMPK) is a major energy regulator that suppresses tumor growth, and 1-(3-chloro-4-((trifluoromethyl)thio)phenyl)-3-(4-(trifluoromethoxy)phenyl)urea (FND-4b) is a novel AMPK activator that inhibits growth and induces apoptosis in colon cancer. The purpose of this project was to test the effects of FND-4b on AMPK activation, proliferation, and apoptosis in breast cancer with a particular emphasis on TNBC.

Materials and methods

(i) Estrogen-receptor positive breast cancer (ER+BC; MCF-7, and T-47D), TNBC (MDA-MB-231 and HCC-1806), and breast cancer stem cells were treated with FND-4b for 24h. Immunoblot analysis assessed AMPK, acetyl-CoA carboxylase (ACC), ribosomal protein S6, cyclin D1, and cleaved PARP. (ii) Sulforhodamine B growth assays were performed after treating ER+BC and TNBC cells with FND-4b for 72h. Proliferation was also assessed by counting cells after 72h of FND-4b treatment. (iii) Cell death ELISA assays were performed after treating ER+BC and TNBC cells with FND-4b for 72h.

Results

(i) FND-4b increased AMPK activation with concomitant decreases in ACC activity, phosphorylated S6, and cyclin D1 in all subtypes. (ii) FND-4b decreased proliferation in all cells, while dose-dependent growth decreases were found in ER+BC and TNBC. (iii) Increases in apoptosis were observed in ER+BC and the MDA-MB-231 cell line with FND-4b treatment.

Conclusions

Our findings indicate that FND-4b decreases proliferation for a variety of breast cancers by activating AMPK and has notable effects on TNBC. The growth reductions were mediated through decreases in fatty acid synthesis (ACC), mTOR signaling (S6), and cell cycle flux (cyclin D1). ER+BC cells were more susceptible to FND-4b-induced apoptosis, but MDA-MB-231 cells still underwent apoptosis with higher dose treatment. Further development of FND compounds could result in a novel therapeutic for TNBC.

Synthetic energy sensor AMPfret deciphers adenylate-dependent AMPK activation mechanism

AMP-activated protein kinase AMPK senses and regulates cellular energy state. AMPK activation by increasing AMP and ADP concentrations involves a conformational switch within the heterotrimeric complex. This is exploited here for the construction of a synthetic sensor of cellular energetics and allosteric AMPK activation, AMPfret. Based on engineered AMPK fused to fluorescent proteins, the sensor allows direct, real-time readout of the AMPK conformational state by fluorescence resonance energy transfer (FRET). AMPfret faithfully and dynamically reports the binding of AMP and ADP to AMPK γ-CBS sites, competed by Mg²⁺-free ATP. FRET signals correlate with activation of AMPK by allosteric mechanisms and protection from dephosphorylation, attributed here to specific CBS sites, but does not require activation loop phosphorylation. Moreover, AMPfret detects binding of pharmacological compounds to the AMPK α/β-ADaM site enabling activator screening. Cellular assays demonstrate that AMPfret is applicable in vivo for spatiotemporal analysis of energy state and allosteric AMPK activation.

AMP-activated protein kinase AMPK senses and regulates cellular energy state. Here the authors engineer a synthetic sensor, AMPfret, that allows direct, real-time readout of the AMPK conformational state by fluorescence resonance energy transfer (FRET).

AMPK is associated with the beneficial effects of antidiabetic agents on cardiovascular diseases

Diabetics have higher morbidity and mortality in cardiovascular disease (CVD). A variety of antidiabetic agents are available for clinical choice. Cardiovascular (CV) safety assessment of these agents is crucial in addition to hypoglycemic effect before clinical prescription. Adenosine 5'-monophosphate-activated protein kinase (AMPK) is an important cell energy sensor, which plays an important role in regulating myocardial energy metabolism, reducing ischemia and ischemia/reperfusion (I/R) injury, improving heart failure (HF) and ventricular remodeling, ameliorating vascular endothelial dysfunction, antichronic inflammation, anti-apoptosis, and regulating autophagy. In this review, we summarized the effects of antidiabetic agents to CVD according to basic and clinical research evidence and put emphasis on whether these agents can play roles in CV system through AMPK-dependent signaling pathways. Metformin has displayed definite CV benefits related to AMPK. Sodium-glucose cotransporter 2 inhibitors also demonstrate sufficient clinical evidence for CV protection, but the mechanisms need further exploration. Glucagon-likepeptide1 analogs, dipeptidyl peptidase-4 inhibitors, α-glucosidase inhibitors and thiazolidinediones also show some AMPK-dependent CV benefits. Sulfonylureas and meglitinides may be unfavorable to CV system. AMPK is becoming a promising target for the treatment of diabetes, metabolic syndrome and CVD. But there are still some questions to be answered.

Identification of microRNAs for regulating adenosine monophosphate-activated protein kinase expression in immature boar Sertoli cells in vitro

Adenosine monophosphate-activated protein kinase (AMPK) plays a key role in cellular energy homeostasis and cell proliferation. MicroRNAs (miRNAs) function as posttranscriptional regulators of gene expression in biological processes. It is unclear to whether miRNAs are involved in AMPK-regulated Sertoli cell (SC) proliferation. To further understand the regulation of miRNAs in the immature boar SC proliferation, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) was added to activate AMPK. By an Illumina small RNA deep sequencing, we obtained sequences and relative expression levels of 272 known mature miRNAs, among which 9 miRNAs were significantly upregulated whereas 16 miRNAs were downregulated following the AICAR treatment. The results identified 38 conserved miRNAs, with 8 significantly downregulated miRNAs whereas no upregulated miRNAs. Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analyses suggested that miR-1285 was involved in many activities and pathways associated with cell proliferation via targeting on AMPKα2. We validated that AICAR significantly downregulated miR-1285 level in SCs. Transfection of miR-1285 mimic increased the SC viability and cell cycle progression but reduced AMPKα2 mRNA and protein levels, indicating that miR-1285 is involved in the immature boar SC proliferation via downregulating AMPKα2 expression.

Chemical genetic screen identifies Gapex-5/GAPVD1 and STBD1 as novel AMPK substrates

AMP-activated protein kinase (AMPK) is a key regulator of cellular energy homeostasis, acting as a sensor of energy and nutrient status. As such, AMPK is considered a promising drug target for treatment of medical conditions particularly associated with metabolic dysfunctions. To better understand the downstream effectors and physiological consequences of AMPK activation, we have employed a chemical genetic screen in mouse primary hepatocytes in an attempt to identify novel AMPK targets. Treatment of hepatocytes with a potent and specific AMPK activator 991 resulted in identification of 65 proteins phosphorylated upon AMPK activation, which are involved in a variety of cellular processes such as lipid/glycogen metabolism, vesicle trafficking, and cytoskeleton organisation. Further characterisation and validation using mass spectrometry followed by immunoblotting analysis with phosphorylation site-specific antibodies identified AMPK-dependent phosphorylation of Gapex-5 (also known as GTPase-activating protein and VPS9 domain-containing protein 1 (GAPVD1)) on Ser902 in hepatocytes and starch-binding domain 1 (STBD1) on Ser175 in multiple cells/tissues. As new promising roles of AMPK as a key metabolic regulator continue to emerge, the substrates we identified could provide new mechanistic and therapeutic insights into AMPK-activating drugs in the liver.

Perilla frutescens Sprout Extract Protect Renal Mesangial Cell Dysfunction against High Glucose by Modulating AMPK and NADPH Oxidase Signaling

Perilla frutescens (L.) Britt. var. japonica (Hassk.) Hara (PF), is a medical herb of the Lamiaceae family. We have previously reported that the PF sprout extract (PFSE) is effective in treating hyperglycemia. However, the role of PFSE on glomerular mesangial cells (MCs) proliferation and the extracellular matrix (ECM) accumulation in a diabetic condition are still unclear. Therefore, in this study, we have investigated the role of PFSE on cell proliferation and ECM accumulation in murine glomerular MCs (MMCs), cultured under a high glucose (HG) condition. PFSE treatment attenuated HG-induced MMCs proliferation and hypertrophy. Moreover, the HG-induced ECM protein, collagen IV and fibronectin, overexpression was abolished by the PFFSE treatment. In addition, PFSE inhibited reactive oxygen species (ROS) overproduction and NOX2 and NOX4 expression in MMCs under a HG condition. Our data further revealed the involvement of mesangial cell damage in AMP-activated kinase (AMPK) activation. PFSE strongly activated AMPK in MMCs under hyperglycemic conditions. These results suggest that PFSE inhibits HG-medicated MC fibrosis through suppressing the activation of NOX2/4 and the AMPK activation mechanism. PFSE may be useful for the prevention or treatment of diabetic nephropathy.

Unpacking the Pathogen Box-An Open Source Tool for Fighting Neglected Tropical Disease

The Pathogen Box is a 400-strong collection of drug-like compounds, selected for their potential against several of the world's most important neglected tropical diseases, including trypanosomiasis, leishmaniasis, cryptosporidiosis, toxoplasmosis, filariasis, schistosomiasis, dengue virus and trichuriasis, in addition to malaria and tuberculosis. This library represents an ensemble of numerous successful drug discovery programmes from around the globe, aimed at providing a powerful resource to stimulate open source drug discovery for diseases threatening the most vulnerable communities in the world. This review seeks to provide an in-depth analysis of the literature pertaining to the compounds in the Pathogen Box, including structure-activity relationship highlights, mechanisms of action, related compounds with reported activity against different diseases, and, where appropriate, discussion on the known and putative targets of compounds, thereby providing context and increasing the accessibility of the Pathogen Box to the drug discovery community.

The role of chamaejasmine in cellular apoptosis and autophagy in MG-63 cells

Background: Osteosarcoma (OS) is the most common malignant neoplasm in children and adolescents with a very high propensity for local invasion and poor response to current therapy. Anti-cancer effect of chamaejasmine is newly discovered from Stellera chamaejasmine L. Our study focuses on investigating the effect of chamaejasmine on the cellular apoptosis, proliferation, autophagy, and the underlying mechanisms in MG-63.

Methods: Our study investigated the concentration of chamaejasmine in MG-63 cells by MTT and verified that chamaejasmine inhibited cell invasion by transwell. We also used Hoechst staining as well as apoptotic associated-proteins in MG-63 cells. Meanwhile, we also detected the lysophagesome and autophagsome by Lysotracker. Adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) knockdown was performed with siRNA.

Results: Our results show that chamaejasmine exerts cellular growth inhibition, pro-apoptotic and pro-autophagic effect via activating AMPK in MG-63 cells. Furthermore, chamaejasmine significantly increases autophagic cell via the inhibition of mammalian target of rapamycin (mTOR) and activation of AMPK signaling pathways. Administrated with chamaejasmine also induces reactive oxygen species (ROS) generation, indicating cross-talking between these two primary modes of programmed cell death.

Conclusion: Our results show that chamaejasmine promotes apoptosis and autophagy by activating AMPK/mTOR signaling pathways with involvement of ROS in MG-63 cells. Chamaejasmine is a promising anti-cancer agent in OS treatment, and further studies are needed to confirm its efficacy and safety in vivo or other cancer cells.

Manipulation and Measurement of AMPK Activity in Pancreatic Islets

The role of the energy sensor AMPK-activated protein kinase (AMPK) in the insulin-secreting β-cell remains unclear and a subject of intense research. With this chapter, we aim to provide a detailed description of the methods that our group routinely applies to the study of AMPK function in mouse and human pancreatic islets. Thus, we provide detailed protocols to isolate and/or culture mouse and human islets, to modulate and measure AMPK activity in isolated islets, and to evaluate its impact on islet function.

Identification of Novel Therapeutic Targets for Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are fatal diseases; however, their pathogenesis still remains to be elucidated. We have recently screened novel pathogenic molecules and have performed drug discovery targeting those molecules. Pulmonary artery smooth muscle cells (PASMCs) in patients with PAH (PAH-PASMCs) have high proliferative properties like cancer cells, which leads to thickening and narrowing of distal pulmonary arteries. Thus, we conducted a comprehensive analysis of PAH-PASMCs and lung tissues to search for novel pathogenic proteins. We validated the pathogenic role of the selected proteins by using tissue-specific knockout mice. To confirm its clinical significance, we used patient-derived blood samples to evaluate the potential as a biomarker for diagnosis and prognosis. Finally, we conducted a high throughput screening and found inhibitors for the pathogenic proteins.

Role of AMPK and PPARα in the anti-skin cancer effects of ursolic acid

The phytonutrient ursolic acid (UA), present in apples, rosemary, and other plant sources, has anti-cancer properties in a number of systems, including skin cancers. However, few reports have examined upstream mechanisms by which UA may prevent or treat cancer. Recent reports have indicated UA induces death of cancer cell lines via AMP-activated protein kinase (AMPK), an energy-sensing kinase which possesses both pro-metabolic and anti-cancer effects. Other studies have shown UA activates peroxisome proliferator activated receptor α (PPARα) and the glucocorticoid receptor (GR). Here, we found the cytotoxic effect of UA in skin carcinoma cells required AMPK activation. In addition, two inhibitors of PPARα partially reversed the cytotoxic effects of UA, suggesting its effects are at least partially mediated through this receptor. Finally, inhibition of the GR did not reverse the effects of UA nor did this compound bind the GR under the conditions of experiments performed. Overall, studies elucidating the anti-cancer effects of UA may allow for the development of more potent analogues utilizing similar mechanisms. These studies may also reveal the mediators of any possible side effects or resistance mechanisms to UA therapy.

AMPK activation regulates P-body dynamics in mouse sensory neurons in vitro and in vivo

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AMPK activators increase P-body formation in DRG neurons in vitro.

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Peripheral nerve injury decreases P-bodies in mouse DRG neurons.

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Treatment with metformin restores normal P-body numbers in DRG neurons from nerve injured mice.

Increased mRNA translation in sensory neurons following peripheral nerve injury contributes to the induction and maintenance of chronic neuropathic pain. Metformin, a common anti-diabetic drug and an activator of AMP-activated protein kinase (AMPK), inhibits cap-dependent mRNA translation and reverses mechanical hypersensitivity caused by a neuropathic injury in both mice and rats. P-bodies are RNA granules that comprise sites for metabolizing mRNA through the process of de-capping followed by RNA decay. These RNA granules may also sequester mRNAs for storage. We have previously demonstrated that induction of cap-dependent translation in cultured trigeminal ganglion (TG) neurons decreases P-body formation and AMPK activators increase P-body formation. Here we examined the impact of AMPK activation on protein synthesis and P-body formation in vitro and in vivo on mouse dorsal root ganglion (DRG) neurons. We demonstrate that AMPK activators inhibit nascent protein synthesis and increase P-body formation in DRG neurons. We also demonstrate that mice with a spared-nerve injury (SNI) show decreased P-bodies in the DRG, consistent with increased mRNA translation resulting from injury. Metformin treatment normalizes this effect in SNI mice and increases P-body formation in sham animals. These findings indicate that P-bodies are dynamically regulated by nerve injury in vivo and this effect can be regulated via AMPK activation.

Structures of AMP-activated protein kinase bound to novel pharmacological activators in phosphorylated, non-phosphorylated, and nucleotide-free states

AMP-activated protein kinase (AMPK) is an attractive therapeutic target for managing metabolic diseases. A class of pharmacological activators, including Merck 991, binds the AMPK ADaM site, which forms the interaction surface between the kinase domain (KD) of the α-subunit and the carbohydrate-binding module (CBM) of the β-subunit. Here, we report the development of two new 991-derivative compounds, R734 and R739, which potently activate AMPK in a variety of cell types, including β₂-specific skeletal muscle cells. Surprisingly, we found that they have only minor effects on direct kinase activity of the recombinant α₁β₂γ₁ isoform yet robustly enhance protection against activation loop dephosphorylation. This mode of activation is reminiscent of that of ADP, which activates AMPK by binding to the nucleotide-binding sites in the γ-subunit, more than 60 Å away from the ADaM site. To understand the mechanisms of full and partial AMPK activation, we determined the crystal structures of fully active phosphorylated AMPK α₁β₁γ₁ bound to AMP and R734/R739 as well as partially active nonphosphorylated AMPK bound to R734 and AMP and phosphorylated AMPK bound to R734 in the absence of added nucleotides at <3-Å resolution. These structures and associated analyses identified a novel conformational state of the AMPK autoinhibitory domain associated with partial kinase activity and provide new insights into phosphorylation-dependent activation loop stabilization in AMPK.

AMP-Activated Protein Kinase as a Key Trigger for the Disuse-Induced Skeletal Muscle Remodeling

Molecular mechanisms that trigger disuse-induced postural muscle atrophy as well as myosin phenotype transformations are poorly studied. This review will summarize the impact of 5′ adenosine monophosphate -activated protein kinase (AMPK) activity on mammalian target of rapamycin complex 1 (mTORC1)-signaling, nuclear-cytoplasmic traffic of class IIa histone deacetylases (HDAC), and myosin heavy chain gene expression in mammalian postural muscles (mainly, soleus muscle) under disuse conditions, i.e., withdrawal of weight-bearing from ankle extensors. Based on the current literature and the authors’ own experimental data, the present review points out that AMPK plays a key role in the regulation of signaling pathways that determine metabolic, structural, and functional alternations in skeletal muscle fibers under disuse.