Signaling kinase AMPK activates stress-promoted transcription via histone H2B phosphorylation

Molecular adaptations to heat stress in the thermophilic ant genus Cataglyphis

Over the last decade, increasing attention has been paid to the molecular adaptations used by organisms to cope with thermal stress. However, to date, few studies have focused on thermophilic species living in hot, arid climates. In this study, we explored molecular adaptations to heat stress in the thermophilic ant genus Cataglyphis, one of the world's most thermotolerant animal taxa. We compared heat tolerance and gene expression patterns across six Cataglyphis species from distinct phylogenetic groups that live in different habitats and experience different thermal regimes. We found that all six species had high heat tolerance levels with critical thermal maxima (CT_max ) ranging from 43℃ to 45℃ and a median lethal temperature (LT50) ranging from 44.5℃ to 46.8℃. Transcriptome analyses revealed that, although the number of differentially expressed genes varied widely for the six species (from 54 to 1118), many were also shared. Functional annotation of the differentially expressed and co-expressed genes showed that the biological pathways involved in heat-shock responses were similar among species and were associated with four major processes: the regulation of transcriptional machinery and DNA metabolism; the preservation of proteome stability; the elimination of toxic residues; and the maintenance of cellular integrity. Overall, our results suggest that molecular responses to heat stress have been evolutionarily conserved in the ant genus Cataglyphis and that their diversity may help workers withstand temperatures close to their physiological limits.

Epigenetic Regulation of Autophagy Beyond the Cytoplasm: A Review

Autophagy is a highly conserved catabolic process induced under various stress conditions to protect the cell from harm and allow survival in the face of nutrient- or energy-deficient states. Regulation of autophagy is complex, as cells need to adapt to a continuously changing microenvironment. It is well recognized that the AMPK and mTOR signaling pathways are the main regulators of autophagy. However, various other signaling pathways have also been described to regulate the autophagic process. A better understanding of these complex autophagy regulatory mechanisms will allow the discovery of new potential therapeutic targets. Here, we present a brief overview of autophagy and its regulatory pathways with emphasis on the epigenetic control mechanisms.

From the (Epi)Genome to Metabolism and Vice Versa; Examples from Hematologic Malignancy

Hematologic malignancies comprise a heterogeneous group of neoplasms arising from hematopoietic cells or their precursors and most commonly presenting as leukemias, lymphomas, and myelomas. Genetic analyses have uncovered recurrent mutations which initiate or accumulate in the course of malignant transformation, as they provide selective growth advantage to the cell. These include mutations in genes encoding transcription factors and epigenetic regulators of metabolic genes, as well as genes encoding key metabolic enzymes. The resulting alterations contribute to the extensive metabolic reprogramming characterizing the transformed cell, supporting its increased biosynthetic needs and allowing it to withstand the metabolic stress that arises as a consequence of increased metabolic rates and changes in its microenvironment. Interestingly, this cross-talk is bidirectional, as metabolites also signal back to the nucleus and, via their widespread effects on modulating epigenetic modifications, shape the chromatin landscape and the transcriptional programs of the cell. In this article, we provide an overview of the main metabolic changes and relevant genetic alterations that characterize malignant hematopoiesis and discuss how, in turn, metabolites regulate epigenetic events during this process. The aim is to illustrate the intricate interrelationship between the genome (and epigenome) and metabolism and its relevance to hematologic malignancy.

AMPK and Pulmonary Hypertension: Crossroads Between Vasoconstriction and Vascular Remodeling

Pulmonary hypertension (PH) is a debilitating and life-threatening disease characterized by increased blood pressure within the pulmonary arteries. Adenosine monophosphate-activated protein kinase (AMPK) is a heterotrimeric serine-threonine kinase that contributes to the regulation of metabolic and redox signaling pathways. It has key roles in the regulation of cell survival and proliferation. The role of AMPK in PH is controversial because both inhibition and activation of AMPK are preventive against PH development. Some clinical studies found that metformin, the first-line antidiabetic drug and the canonical AMPK activator, has therapeutic efficacy during treatment of early-stage PH. Other study findings suggest the use of metformin is preferentially beneficial for treatment of PH associated with heart failure with preserved ejection fraction (PH-HFpEF). In this review, we discuss the "AMPK paradox" and highlight the differential effects of AMPK on pulmonary vasoconstriction and pulmonary vascular remodeling. We also review the effects of AMPK activators and inhibitors on rescue of preexisting PH in animals and include a discussion of gender differences in the response to metformin in PH.

Light-Activation of DNA-Methyltransferases

5-Methylcytosine (5mC), the central epigenetic mark of mammalian DNA, plays fundamental roles in chromatin regulation. 5mC is written onto genomes by DNA methyltransferases (DNMT), and perturbation of this process is an early event in carcinogenesis. However, studying 5mC functions is limited by the inability to control individual DNMTs with spatiotemporal resolution in vivo. We report light-control of DNMT catalysis by genetically encoding a photocaged cysteine as a catalytic residue. This enables translation of inactive DNMTs, their rapid activation by light-decaging, and subsequent monitoring of de novo DNA methylation. We provide insights into how cancer-related DNMT mutations alter de novo methylation in vivo, and demonstrate local and tuneable cytosine methylation by light-controlled DNMTs fused to a programmable transcription activator-like effector domain targeting pericentromeric satellite-3 DNA. We further study early events of transcriptome alterations upon DNMT-catalyzed cytosine methylation. Our study sets a basis to dissect the order and kinetics of diverse chromatin-associated events triggered by normal and aberrant DNA methylation.

Islet Epigenetic Impacts on β-Cell Identity and Function

The development and maintenance of differentiation is vital to the function of mature cells. Terminal differentiation is achieved by locking in the expression of genes essential for the function of those cells. Gene expression and its memory through generations of cell division is controlled by transcription factors and a host of epigenetic marks. In type 2 diabetes, β cells have altered gene expression compared to controls, accompanied by altered chromatin marks. Mutations, diet, and environment can all disrupt the implementation and preservation of the distinctive β-cell transcriptional signature. Understanding of the full complement of genomic control in β cells is still nascent. This article describes the known effects of histone marks and variants, DNA methylation, how they are regulated in the β cell, and how they affect cell-fate specification, maintenance, and lineage propagation. © 2021 American Physiological Society. Compr Physiol 11:1-18, 2021.

Metabolic reprogramming and epigenetic modifications on the path to cancer

Metabolic rewiring and epigenetic remodeling, which are closely linked and reciprocally regulate each other, are among the well-known cancer hallmarks. Recent evidence suggests that many metabolites serve as substrates or cofactors of chromatin-modifying enzymes as a consequence of the translocation or spatial regionalization of enzymes or metabolites. Various metabolic alterations and epigenetic modifications also reportedly drive immune escape or impede immunosurveillance within certain contexts, playing important roles in tumor progression. In this review, we focus on how metabolic reprogramming of tumor cells and immune cells reshapes epigenetic alterations, in particular the acetylation and methylation of histone proteins and DNA. We also discuss other eminent metabolic modifications such as, succinylation, hydroxybutyrylation, and lactylation, and update the current advances in metabolism- and epigenetic modification-based therapeutic prospects in cancer.

Parental energy-sensing pathways control intergenerational offspring sex determination in the nematode Auanema freiburgensis

BACKGROUND

Environmental stimuli experienced by the parental generation influence the phenotype of subsequent generations (Demoinet et al., Proc Natl Acad Sci U S A 114:E2689-E2698, 2017; Burton et al., Nat Cell Biol 19:252-257, 2017; Agrawal et al., Nature 401:60-63, 1999). The effects of these stimuli on the parental generation may be passed through the germline, but the mechanisms at the basis of this non-Mendelian type of inheritance, their level of conservation, how they lead to adaptive vs non-adaptive, and intergenerational vs transgenerational inheritance are poorly understood. Here we show that modulation of nutrient-sensing pathways in the parental generation of the nematode Auanema freiburgensis regulates phenotypic plasticity of its offspring.

RESULTS

In response to con-specific pheromones indicative of stress, AMP-activated protein kinase (AMPK), mechanistic target of rapamycin complex 1 (mTORC1), and insulin signaling regulate stress resistance and sex determination across one generation, and these effects can be mimicked by pathway modulators. The effectors of these pathways are closely associated with the chromatin, and their regulation affects the chromatin acetylation status in the germline.

CONCLUSION

These results suggest that highly conserved metabolic sensors regulate phenotypic plasticity through regulation of subcellular localization of their effectors, leading to changes in chromatin acetylation and epigenetic status of the germline.

Predictive biomarkers and potential drug combinations of epi-drugs in cancer therapy

Epigenetics studies heritable genomic modifications that occur with the participation of epigenetic modifying enzymes but without alterations of the nucleotide structure. Small-molecule inhibitors of these epigenetic modifying enzymes are known as epigenetic drugs (epi-drugs), which can cause programmed death of tumor cells by affecting the cell cycle, angiogenesis, proliferation, and migration. Epi-drugs include histone methylation inhibitors, histone demethylation inhibitors, histone deacetylation inhibitors, and DNA methylation inhibitors. Currently, epi-drugs undergo extensive development, research, and application. Although epi-drugs have convincing anti-tumor effects, the patient's sensitivity to epi-drug application is also a fundamental clinical issue. The development and research of biomarkers for epi-drugs provide a promising direction for screening drug-sensitive patients. Here, we review the predictive biomarkers of 12 epi-drugs as well as the progress of combination therapy with chemotherapeutic drugs or immunotherapy. Further, we discuss the improvement in the development of natural ingredients with low toxicity and low side effects as epi-drugs.

Epigenetic landscape of testis specific histone H2B variant and its influence on sperm function

BACKGROUND

Biological relevance of the major testis specific histone H2B variant (TH2B) in sperm is not fully understood. Studies in TH2A/TH2B double knockout male mice indicate its role in chromatin compaction and male fertility. Additionally, the presence of TH2B and TH2A reportedly generates more dynamic nucleosomes, leading to an open chromatin structure characteristic of transcriptionally active genome. Given that mature human sperm are transcriptionally and translationally inactive, the presence of TH2B in mature sperm is intriguing. To address its role in sperm, we investigated the genome-wide localization of TH2B in sperm of fertile men.

RESULTS

We have identified the genomic loci associated with TH2B in fertile human sperm by ChIP-seq analysis. Bioinformatic analysis revealed ~ 5% sperm genome and 5527 genes to be associated with TH2B. Out of these 105 (1.9%) and 144 (2.6%) genes showed direct involvement in sperm function and early embryogenesis, respectively. Chromosome wide analysis for TH2B distribution indicated its least distribution on X and Y chromosomes and varied distribution on autosomes. TH2B showed relatively higher percentage of gene association on chromosome 4, 18, 3 and 2. TH2B enrichment was more in promoter and gene body region. Gene Ontology (GO) analysis revealed signal transduction and associated kinase activity as the most enriched biological and molecular function, respectively. We also observed the enrichment of TH2B at developmentally important loci, such as HOXA and HOXD and on genes required for normal sperm function, few of which were validated by ChIP-qPCR. The relative expression of these genes was altered in particular subgroup of infertile men showing abnormal chromatin packaging. Chromatin compaction positively correlated with sperm- motility, concentration, viability and with transcript levels of PRKAG2 and CATSPER B.

CONCLUSION

ChIP-seq analysis of TH2B revealed a putative role of TH2B in sperm function and embryo development. Altered expression of TH2B associated genes in infertile individuals with sperm chromatin compaction defects indicates involvement of TH2B in transcriptional regulation of these genes in post meiotic male germ cells. This altered transcriptome may be a consequence or cause of abnormal nuclear remodeling during spermiogenesis.

Gut Microbiota Composition and Epigenetic Molecular Changes Connected to the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder, and its pathogenesis is not fully known. Although there are several hypotheses, such as neuroinflammation, tau hyperphosphorylation, amyloid-β plaques, neurofibrillary tangles, and oxidative stress, none of them completely explain the origin and progression of AD. Emerging evidence suggests that gut microbiota and epigenetics can directly influence the pathogenesis of AD via their effects on multiple pathways, including neuroinflammation, oxidative stress, and amyloid protein. Various gut microbes such as Actinobacteria, Bacteroidetes, E. coli, Firmicutes, Proteobacteria, Tenericutes, and Verrucomicrobia are known to play a crucial role in the pathogenesis of AD. These microbes and their metabolites modulate various physiological processes that contribute to AD pathogenesis, such as neuroinflammation and other inflammatory processes, amyloid deposition, cytokine storm syndrome, altered BDNF and NMDA signaling, impairing neurodevelopmental processes. Likewise, epigenetic markers associated with AD mainly include histone modifications and DNA methylation, which are under the direct control of a variety of enzymes, such as acetylases and methylases. The activity of these enzymes is dependent upon the metabolites generated by the host's gut microbiome, suggesting the significance of epigenetics in AD pathogenesis. It is interesting to know that both gut microbiota and epigenetics are dynamic processes and show a high degree of variation according to diet, stressors, and environmental factors. The bidirectional relation between the gut microbiota and epigenetics suggests that they might work in synchrony to modulate AD representation, its pathogenesis, and progression. They both also provide numerous targets for early diagnostic biomarkers and for the development of AD therapeutics. This review discusses the gut microbiota and epigenetics connection in the pathogenesis of AD and aims to highlight vast opportunities for diagnosis and therapeutics of AD.

AMPKβ1 and AMPKβ2 define an isoform-specific gene signature in human pluripotent stem cells, differentially mediating cardiac lineage specification

AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism that phosphorylates a wide range of proteins to maintain cellular homeostasis. AMPK consists of three subunits: α, β, and γ. AMPKα and β are encoded by two genes, the γ subunit by three genes, all of which are expressed in a tissue-specific manner. It is not fully understood, whether individual isoforms have different functions. Using RNA-Seq technology, we provide evidence that the loss of AMPKβ1 and AMPKβ2 lead to different gene expression profiles in human induced pluripotent stem cells (hiPSCs), indicating isoform-specific function. The knockout of AMPKβ2 was associated with a higher number of differentially regulated genes than the deletion of AMPKβ1, suggesting that AMPKβ2 has a more comprehensive impact on the transcriptome. Bioinformatics analysis identified cell differentiation as one biological function being specifically associated with AMPKβ2. Correspondingly, the two isoforms differentially affected lineage decision toward a cardiac cell fate. Although the lack of PRKAB1 impacted differentiation into cardiomyocytes only at late stages of cardiac maturation, the availability of PRKAB2 was indispensable for mesoderm specification as shown by gene expression analysis and histochemical staining for cardiac lineage markers such as cTnT, GATA4, and NKX2.5. Ultimately, the lack of AMPKβ1 impairs, whereas deficiency of AMPKβ2 abrogates differentiation into cardiomyocytes. Finally, we demonstrate that AMPK affects cellular physiology by engaging in the regulation of hiPSC transcription in an isoform-specific manner, providing the basis for further investigations elucidating the role of dedicated AMPK subunits in the modulation of gene expression.

Signaling-to-chromatin pathways in the immune system

Complex organisms are able to respond to diverse environmental cues by rapidly inducing specific transcriptional programs comprising a few dozen genes among thousands. The highly complex environment within the nucleus-a crowded milieu containing large genomes tightly condensed with histone proteins in the form of chromatin-makes inducible transcription a challenge for the cell, akin to the proverbial needle in a haystack. The different signaling pathways and transcription factors involved in the transmission of information from the cell surface to the nucleus have been readily explored, but not so much the specific mechanisms employed by the cell to ultimately instruct the chromatin changes necessary for a fast and robust transcription activation. Signaling pathways rely on cascades of protein kinases that, in addition to activating transcription factors can also activate the chromatin template by phosphorylating histone proteins, what we refer to as "signaling-to-chromatin." These pathways appear to be selectively employed and especially critical for driving inducible transcription in macrophages and likely in diverse other immune cell populations. Here, we discuss signaling-to-chromatin pathways with potential relevance in diverse immune cell populations together with chromatin related mechanisms that help to "solve" the needle in a haystack challenge of robust chromatin activation and inducible transcription.

PPARα-Selective Antagonist GW6471 Inhibits Cell Growth in Breast Cancer Stem Cells Inducing Energy Imbalance and Metabolic Stress

Breast cancer is the most frequent cancer and the second leading cause of death among women. Triple-negative breast cancer is the most aggressive subtype of breast cancer and is characterized by the absence of hormone receptors and human epithelial growth factor receptor 2. Cancer stem cells (CSCs) represent a small population of tumor cells showing a crucial role in tumor progression, metastasis, recurrence, and drug resistance. The presence of CSCs can explain the failure of conventional therapies to completely eradicate cancer. Thus, to overcome this limit, targeting CSCs may constitute a promising approach for breast cancer treatment, especially in the triple-negative form. To this purpose, we isolated and characterized breast cancer stem cells from a triple-negative breast cancer cell line, MDA-MB-231. The obtained mammospheres were then treated with the specific PPARα antagonist GW6471, after which, glucose, lipid metabolism, and invasiveness were analyzed. Notably, GW6471 reduced cancer stem cell viability, proliferation, and spheroid formation, leading to apoptosis and metabolic impairment. Overall, our findings suggest that GW6471 may be used as a potent adjuvant for gold standard therapies for triple-negative breast cancer, opening the possibility for preclinical and clinical trials for this class of compounds.

Yeast Nuak1 phosphorylates histone H3 threonine 11 in low glucose stress by the cooperation of AMPK and CK2 signaling

Changes in available nutrients are inevitable events for most living organisms. Upon nutritional stress, several signaling pathways cooperate to change the transcription program through chromatin regulation to rewire cellular metabolism. In budding yeast, histone H3 threonine 11 phosphorylation (H3pT11) acts as a marker of low glucose stress and regulates the transcription of nutritional stress-responsive genes. Understanding how this histone modification 'senses' external glucose changes remains elusive. Here, we show that Tda1, the yeast ortholog of human Nuak1, is a direct kinase for H3pT11 upon low glucose stress. Yeast AMP-activated protein kinase (AMPK) directly phosphorylates Tda1 to govern Tda1 activity, while CK2 regulates Tda1 nuclear localization. Collectively, AMPK and CK2 signaling converge on histone kinase Tda1 to link external low glucose stress to chromatin regulation.

Phosphorylation of PDHA by AMPK Drives TCA Cycle to Promote Cancer Metastasis

Cancer metastasis accounts for the major cause of cancer-related deaths. How disseminated cancer cells cope with hostile microenvironments in secondary site for full-blown metastasis is largely unknown. Here, we show that AMPK (AMP-activated protein kinase), activated in mouse metastasis models, drives pyruvate dehydrogenase complex (PDHc) activation to maintain TCA cycle (tricarboxylic acid cycle) and promotes cancer metastasis by adapting cancer cells to metabolic and oxidative stresses. This AMPK-PDHc axis is activated in advanced breast cancer and predicts poor metastasis-free survival. Mechanistically, AMPK localizes in the mitochondrial matrix and phosphorylates the catalytic alpha subunit of PDHc (PDHA) on two residues S295 and S314, which activates the enzymatic activity of PDHc and alleviates an inhibitory phosphorylation by PDHKs, respectively. Importantly, these phosphorylation events mediate PDHc function in cancer metastasis. Our study reveals that AMPK-mediated PDHA phosphorylation drives PDHc activation and TCA cycle to empower cancer cells adaptation to metastatic microenvironments for metastasis.

LKB1 and cancer: The dual role of metabolic regulation

Liver kinase B1 (LKB1) is an essential serine/threonine kinase frequently associated with Peutz-Jeghers syndrome (PJS). In this review, we provide an overview of the role of LKB1 in conferring protection to cancer cells against metabolic stress and promoting cancer cell survival and invasion. This carcinogenic effect contradicts the previous conclusion that LKB1 is a tumor suppressor gene. Here we try to explain the contradictory effect of LKB1 on cancer from a metabolic perspective. Upon deletion of LKB1, cancer cells experience increased energy as well as oxidative stress, thereby causing genomic instability. Meanwhile, mutated LKB1 cooperates with other metabolic regulatory genes to promote metabolic reprogramming that subsequently facilitates adaptation to strong metabolic stress, resulting in development of a more aggressive malignant phenotype. We aim to specifically discuss the contradictory role of LKB1 in cancer by reviewing the mechanism of LKB1 with an emphasis on metabolic stress and metabolic reprogramming.

Transcriptomic signatures of cold adaptation and heat stress in the winter ant (Prenolepis imparis)

Climate change is a serious threat to biodiversity; it is therefore important to understand how animals will react to this stress. Ectotherms, such as ants, are especially sensitive to the climate as the environmental temperature influences myriad aspects of their biology, from optimal foraging time to developmental rate. In this study, we conducted an RNA-seq analysis to identify stress-induced genes in the winter ant (Prenolepis imparis). We quantified gene expression during heat and cold stress relative to a control temperature. From each of our conditions, we sequenced the transcriptome of three individuals. Our de novo assembly included 13,324 contigs that were annotated against the nr and SwissProt databases. We performed gene ontology and enrichment analyses to gain insight into the physiological processes involved in the stress response. We identified a total of 643 differentially expressed genes across both treatments. Of these, only seven genes were differentially expressed in the cold-stressed ants, which could indicate that the temperature we chose for trials did not induce a strong stress response, perhaps due to the cold adaptations of this species. Conversely, we found a strong response to heat: 426 upregulated genes and 210 downregulated genes. Of these, ten were expressed at a greater than ten-fold change relative to the control. The transcripts we could identify included those encoding for protein folding genes, heat shock proteins, histones, and Ca2+ ion transport. One of these transcripts, hsc70-4L was found to be under positive selection. We also characterized the functional categories of differentially expressed genes. These candidate genes may be functionally conserved and relevant for related species that will deal with rapid climate change.

SnRK1 regulates chromatin-associated OXS3 family proteins localization through phosphorylation in Arabidopsis thaliana

In plants, SNF1-related protein kinase 1 (SnRK1) senses nutrient and energy status and transduces this information into appropriate responses. Oxidative Stress 3 (OXS3) and family members share a highly conserved putative N-acetyltransferase catalytic domain (ACD). Here, we describe that the ACD contains two candidate SnRK1 recognition motifs and that SnRK1 can interact with most of the OXS3 family proteins. In vitro, SnRK1.1 can phosphorylate OXS3, OXS3b and O3L4, and in vivo promote the translocation of OXS3, OXS3b and O3L6 from the nucleus to the cytoplasm. Phosphorylation sites within the OXS3 ACD affect OXS3 cytoplasmic accumulation, as well as their interactions with SnRK1.1. This suggests that signal transduction from SnRK1 to OXS3 family proteins, and that SnRK1 can control their activities through phosphorylation-induced nuclear exclusion.

Systematic genetic and proteomic screens during gametogenesis identify H2BK34 methylation as an evolutionary conserved meiotic mark

BACKGROUND

Gametes are highly differentiated cells specialized to carry and protect the parental genetic information. During male germ cell maturation, histone proteins undergo distinct changes that result in a highly compacted chromatin organization. Technical difficulties exclude comprehensive analysis of precise histone mutations during mammalian spermatogenesis. The model organism Saccharomyces cerevisiae possesses a differentiation pathway termed sporulation which exhibits striking similarities to mammalian spermatogenesis. This study took advantage of this yeast pathway to first perform systematic mutational and proteomics screens on histones, revealing amino acid residues which are essential for the formation of spores.

METHODS

A systematic mutational screen has been performed on the histones H2A and H2B, generating ~ 250 mutants using two genetic backgrounds and assessing their ability to form spores. In addition, histones were purified at key stages of sporulation and post-translational modifications analyzed by mass spectrometry.

RESULTS

The mutation of 75 H2A H2B residues affected sporulation, many of which were localized to the nucleosome lateral surface. The use of different genetic backgrounds confirmed the importance of many of the residues, as 48% of yeast histone mutants exhibited impaired formation of spores in both genetic backgrounds. Extensive proteomic analysis identified 67 unique post-translational modifications during sporulation, 27 of which were previously unreported in yeast. Furthermore, 33 modifications are located on residues that were found to be essential for efficient sporulation in our genetic mutation screens. The quantitative analysis of these modifications revealed a massive deacetylation of all core histones during the pre-meiotic phase and a close interplay between H4 acetylation and methylation during yeast sporulation. Methylation of H2BK37 was also identified as a new histone marker of meiosis and the mouse paralog, H2BK34, was also enriched for methylation during meiosis in the testes, establishing conservation during mammalian spermatogenesis.

CONCLUSION

Our results demonstrate that a combination of genetic and proteomic approaches applied to yeast sporulation can reveal new aspects of chromatin signaling pathways during mammalian spermatogenesis.

Cellular toxicity of the metabolic inhibitor 2-deoxyglucose and associated resistance mechanisms

Most malignant cells display increased glucose absorption and metabolism compared to surrounding tissues. This well-described phenomenon results from a metabolic reprogramming occurring during transformation, that provides the building blocks and supports the high energetic cost of proliferation by increasing glycolysis. These features led to the idea that drugs targeting glycolysis might prove efficient in the context of cancer treatment. One of these drugs, 2-deoxyglucose (2-DG), is a synthetic glucose analog that can be imported into cells and interfere with glycolysis and ATP generation. Its preferential targeting to sites of cell proliferation is supported by the observation that a derived molecule, 2-fluoro-2-deoxyglucose (FDG) accumulates in tumors and is used for cancer imaging. Here, we review the toxicity mechanisms of this drug, from the early-described effects on glycolysis to its other cellular consequences, including inhibition of protein glycosylation and endoplasmic reticulum stress, and its interference with signaling pathways. Then, we summarize the current data on the use of 2-DG as an anti-cancer agent, especially in the context of combination therapies, as novel 2-DG-derived drugs are being developed. We also show how the use of 2-DG helped to decipher glucose-signaling pathways in yeast and favored their engineering for biotechnologies. Finally, we discuss the resistance strategies to this inhibitor that have been identified in the course of these studies and which may have important implications regarding a medical use of this drug.

GLUT3 induced by AMPK/CREB1 axis is key for withstanding energy stress and augments the efficacy of current colorectal cancer therapies

Cancer cells are usually characterized by hyperactive glucose metabolism, which can often lead to glucose scarcity; thus, alternative pathways to rewire cancer metabolism are required. Here, we demonstrated that GLUT3 was highly expressed in colorectal cancer (CRC) and negatively linked to CRC patient outcomes, whereas GLUT1 was not associated with CRC prognosis. Under glucose-limiting conditions, GLUT3 expedited CRC cell growth by accelerating glucose input and fuelling nucleotide synthesis. Notably, GLUT3 had a greater impact on cell growth than GLUT1 under glucose-limiting stress. Mechanistically, low-glucose stress dramatically upregulated GLUT3 via the AMPK/CREB1 pathway. Furthermore, high GLUT3 expression remarkably increased the sensitivity of CRC cells to treatment with vitamin C and vitamin C-containing regimens. Together, the results of this study highlight the importance of the AMPK/CREB1/GLUT3 pathway for CRC cells to withstand glucose-limiting stress and underscore the therapeutic potential of vitamin C in CRC with high GLUT3 expression.

Nutrient Sensing by Histone Marks: Reading the Metabolic Histone Code Using Tracing, Omics, and Modeling

Several metabolites serve as substrates for histone modifications and communicate changes in the metabolic environment to the epigenome. Technologies such as metabolomics and proteomics have allowed us to reconstruct the interactions between metabolic pathways and histones. These technologies have shed light on how nutrient availability can have a dramatic effect on various histone modifications. This metabolism-epigenome cross talk plays a fundamental role in development, immune function, and diseases like cancer. Yet, major challenges remain in understanding the interactions between cellular metabolism and the epigenome. How the levels and fluxes of various metabolites impact epigenetic marks is still unclear. Discussed herein are recent applications and the potential of systems biology methods such as flux tracing and metabolic modeling to address these challenges and to uncover new metabolic-epigenetic interactions. These systems approaches can ultimately help elucidate how nutrients shape the epigenome of microbes and mammalian cells.

Functional Interplay between Histone H2B ADP-Ribosylation and Phosphorylation Controls Adipogenesis

Although ADP-ribosylation of histones by PARP-1 has been linked to genotoxic stress responses, its role in physiological processes and gene expression has remained elusive. We found that NAD⁺-dependent ADP-ribosylation of histone H2B-Glu35 by small nucleolar RNA (snoRNA)-activated PARP-1 inhibits AMP kinase-mediated phosphorylation of adjacent H2B-Ser36, which is required for the proadipogenic gene expression program. The activity of PARP-1 on H2B requires NMNAT-1, a nuclear NAD⁺ synthase, which directs PARP-1 catalytic activity to Glu and Asp residues. ADP-ribosylation of Glu35 and the subsequent reduction of H2B-Ser36 phosphorylation inhibits the differentiation of adipocyte precursors in cultured cells. Parp1 knockout in preadipocytes in a mouse lineage-tracing genetic model increases adipogenesis, leading to obesity. Collectively, our results demonstrate a functional interplay between H2B-Glu35 ADP-ribosylation and H2B-Ser36 phosphorylation that controls adipogenesis.

AMPK Enhances Transcription of Selected Nrf2 Target Genes via Negative Regulation of Bach1

5'-AMP-activated protein kinase (AMPK) and the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) are main players in the cellular adaptive response to metabolic and oxidative/xenobiotic stress, respectively. AMPK does not only balance the rate of fuel catabolism versus anabolism but also emerges as regulator of gene expression. We here examined the influence of AMPK on Nrf2-dependent gene transcription and the potential interplay of the two cellular stress hubs. Using gene expression analyses in wt and AMPKα1 -/- or Nrf2 -/- mouse embryonal fibroblasts, we could show that AMPK only affected a portion of the entire of Nrf2-dependent transcriptome upon exposure to the Nrf2 activator sulforaphane (Sfn). Focusing on selected genes with positive regulation by Nrf2 and either positive or no further regulation by AMPK, we revealed that altered Nrf2 levels could not account for the distinct extent of transactivation of certain Nrf2 targets in wt and AMPK -/- cells (assessed by immunoblot). FAIRE-qPCR largely excluded distinct chromatin accessibility of selected Nrf2-responsive antioxidant response elements (ARE) within the regulatory gene regions in wt and AMPK-/- cells. However, expression analyses and ChIP-qPCR showed that in AMPK-/- cells, levels of BTB and CNC homology 1 (Bach1), a competitor of Nrf2 for ARE sites with predominant repressor function, were higher, and Bach1 also bound to a greater relative extent to the examined ARE sites when compared to Nrf2. The negative influence of AMPK on Bach1 was confirmed by pharmacological and genetic approaches and occurred at the level of mRNA synthesis. Overall, the observed AMPK-mediated boost in transactivation of a subset of Nrf2 target genes involves downregulation of Bach1 and subsequent favored binding of activating Nrf2 over repressing Bach1 to the examined ARE sites.

Insight on Transcriptional Regulation of the Energy Sensing AMPK and Biosynthetic mTOR Pathway Genes

The Adenosine Monophosphate-activated Protein Kinase (AMPK) and the Mechanistic Target of Rapamycin (mTOR) are two evolutionarily conserved kinases that together regulate nearly every aspect of cellular and systemic metabolism. These two kinases sense cellular energy and nutrient levels that in turn are determined by environmental nutrient availability. Because AMPK and mTOR are kinases, the large majority of studies remained focused on downstream substrate phosphorylation by these two proteins, and how AMPK and mTOR regulate signaling and metabolism in normal and disease physiology through phosphorylation of their substrates. Compared to the wealth of information known about the signaling and metabolic pathways modulated by these two kinases, much less is known about how the transcription of AMPK and mTOR pathway genes themselves are regulated, and the extent to which AMPK and mTOR regulate gene expression to cause durable changes in phenotype. Acute modification of cellular systems can be achieved through phosphorylation, however, induction of chronic changes requires modulation of gene expression. In this review we will assemble evidence from published studies on transcriptional regulation by AMPK and mTOR and discuss about the putative transcription factors that regulate expression of AMPK and mTOR complex genes.

DNA Damage Response and Metabolic Reprogramming in Health and Disease

Nuclear DNA damage contributes to cellular malfunction and the premature onset of age-related diseases, including cancer. Until recently, the canonical DNA damage response (DDR) was thought to represent a collection of nuclear processes that detect, signal and repair damaged DNA. However, recent evidence suggests that beyond nuclear events, the DDR rewires an intricate network of metabolic circuits, fine-tunes protein synthesis, trafficking, and secretion as well as balances growth with defense strategies in response to genotoxic insults. In this review, we discuss how the active DDR signaling mobilizes extranuclear and systemic responses to promote cellular homeostasis and organismal survival in health and disease.

AMPK in microvascular complications of diabetes and the beneficial effects of AMPK activators from plants

BACKGROUND

Diabetes mellitus is a multifactorial disorder with the risk of micro- and macro-vascular complications. High glucose-induced derangements in metabolic pathways are primarily associated with the initiation and progression of secondary complications namely, diabetic nephropathy, neuropathy, and retinopathy. Adenosine monophosphate-activated protein kinase (AMPK) has emerged as an attractive therapeutic target to treat various metabolic disorders including diabetes mellitus. It is a master metabolic regulator that helps in maintaining cellular energy homeostasis by promoting ATP-generating catabolic pathways and inhibiting ATP-consuming anabolic pathways. Numerous pharmacological and plant-derived bioactive compounds that increase AMP-activated protein kinase activation has shown beneficial effects by mitigating secondary complications namely retinopathy, nephropathy, and neuropathy.

PURPOSE

The purpose of this review is to highlight current knowledge on the role of AMPK and its activators from plant origin in diabetic microvascular complications.

METHODS

Search engines such as Google Scholar, PubMed, Science Direct and Web of Science are used to extract papers using relevant key words. Papers mainly focusing on the role of AMPK and AMPK activators from plant origin in diabetic nephropathy, retinopathy, and neuropathy was chosen to be highlighted.

RESULTS

According to results, decrease in AMPK activation during diabetes play a causative role in the pathogenesis of diabetic microvascular complications. Some of the plant-derived bioactive compounds were beneficial in restoring AMPK activity and ameliorating diabetic microvascular complications.

CONCLUSION

AMPK activators from plant origin are beneficial in mitigating diabetic microvascular complications. These pieces of evidence will be helpful in the development of AMPK-centric therapies to mitigate diabetic microvascular complications.

Phosphorylated Acetyl-CoA Carboxylase Is Associated with Clinical Benefit with Regorafenib in Relapsed Glioblastoma: REGOMA Trial Biomarker Analysis

PURPOSE

Preclinical studies show that antiangiogenic therapy exacerbates tumor glycolysis and activates liver kinase B1/AMP kinase (AMPK), a pathway involved in the regulation of tumor metabolism. We investigated whether certain metabolism-related in situ biomarkers could predict benefit to regorafenib in the phase II randomized REGOMA trial.

PATIENTS AND METHODS

IHC and digital pathology analysis were used to investigate the expression in glioblastoma (GBM) sections of monocarboxylate transporter 1 and 4 (MCT1 and MCT4), associated with OXPHOS and glycolysis, respectively, phosphorylated AMPK (pAMPK), and phosphorylated acetyl-CoA carboxylase (pACC), a canonical target of AMPK activity. The status of each biomarker was associated with clinical endpoints, including overall survival (OS) and progression-free survival (PFS) in patients with relapsed GBM treated either with regorafenib or lomustine.

RESULTS

Between November 2015 and February 2017, 119 patients were enrolled (n = 59 regorafenib and n = 60 lomustine) and stratified for surgery at recurrence, and baseline characteristics were balanced. Biomarker analysis was performed in 84 patients (71%), including 42 patients of the regorafenib arm and 42 patients of the lomustine arm. Among all markers analyzed, only pACC showed predictive value in terms of OS. In fact, median OS was 9.3 months [95% confidence interval (CI), 5.6-13.2] for regorafenib and 5.5 months (95% CI, 4.2-6.6) for lomustine for pACC-positive patients, HR, 0.37 (95% CI, 0.20-0.70); log rank P = 0.0013; test for interaction = 0.0453. No statistically significant difference was demonstrated for PFS according to pACC status.

CONCLUSIONS

We found that AMPK pathway activation is associated with clinical benefit from treatment with regorafenib in relapsed GBM.

GsSnRK1 interplays with transcription factor GsERF7 from wild soybean to regulate soybean stress resistance

Although the function and regulation of SnRK1 have been studied in various plants, its molecular mechanisms in response to abiotic stresses are still elusive. In this work, we identified an AP2/ERF domain-containing protein (designated GsERF7) interacting with GsSnRK1 from a wild soybean cDNA library. GsERF7 gene expressed dominantly in wild soybean roots and was responsive to ethylene, salt, and alkaline. GsERF7 bound GCC cis-acting element and could be phosphorylated on S36 by GsSnRK1. GsERF7 phosphorylation facilitated its translocation from cytoplasm to nucleus and enhanced its transactivation activity. When coexpressed in the hairy roots of soybean seedlings, GsSnRK1(wt) and GsERF7(wt) promoted plants to generate higher tolerance to salt and alkaline stresses than their mutated species, suggesting that GsSnRK1 may function as a biochemical and genetic upstream kinase of GsERF7 to regulate plant adaptation to environmental stresses. Furthermore, the altered expression patterns of representative abiotic stress-responsive and hormone-synthetic genes were determined in transgenic soybean hairy roots after stress treatments. These results will aid our understanding of molecular mechanism of how SnRK1 kinase plays a cardinal role in regulating plant stress resistances through activating the biological functions of downstream factors.

Causes and Consequences of Variable Tumor Cell Metabolism on Heritable Modifications and Tumor Evolution

When cancer research advanced into the post-genomic era, it was widely anticipated that the sought-after cure will be delivered promptly. Instead, it became apparent that an understanding of cancer genomics, alone, is unable to translate the wealth of information into successful cures. While gene sequencing has significantly improved our understanding of the natural history of cancer and identified candidates for therapeutic targets, it cannot predict the impact of the biological response to therapies. Hence, patients with a common mutational profile may respond differently to the same therapy, due in part to different microenvironments impacting on gene regulation. This complexity arises from a feedback circuit involving epigenetic modifications made to genes by the metabolic byproducts of cancer cells. New insights into epigenetic mechanisms, activated early in the process of carcinogenesis, have been able to describe phenotypes which cannot be inferred from mutational analyses per se. Epigenetic changes can propagate throughout a tumor via heritable modifications that have long-lasting consequences on ensuing phenotypes. Such heritable epigenetic changes can be evoked profoundly by cancer cell metabolites, which then exercise a broad remit of actions across all stages of carcinogenesis, culminating with a meaningful impact on the tumor's response to therapy. This review outlines some of the cross-talk between heritable epigenetic changes and tumor cell metabolism, and the consequences of such changes on tumor progression.

AMPK Regulates Developmental Plasticity through an Endogenous Small RNA Pathway in Caenorhabditis elegans

Caenorhabditis elegans larvae can undergo developmental arrest upon entry into the dauer stage in response to suboptimal growth conditions. Dauer larvae can exit this stage in replete conditions with no reproductive consequence. During this diapause stage, the metabolic regulator AMP-activated protein kinase (AMPK) ensures that the germ line becomes quiescent to maintain germ cell integrity. Animals that lack all AMPK signalling undergo germline hyperplasia upon entering dauer, while those that recover from this stage become sterile. Neuronal AMPK expression in otherwise AMPK-deficient animals is sufficient for germline quiescence and germ cell integrity and its effects are likely mediated through an endogenous small RNA pathway. Upon impairing small RNA biosynthesis, the post-dauer fertility is restored in AMPK mutants. These data suggest that AMPK may function in neurons to relay a message through small RNAs to the germ cells to alter their quiescence in the dauer stage, thus challenging the permeability of the Weismann barrier.

Spatial control of AMPK signaling at subcellular compartments

AMP-activated protein kinase (AMPK) is a master regulator of energy homeostasis that functions to restore the energy balance by phosphorylating its substrates during altered metabolic conditions. AMPK activity is tightly controlled by diverse regulators including its upstream kinases LKB1 and CaMKK2. Recent studies have also identified the localization of AMPK at different intracellular compartments as another key mechanism for regulating AMPK signaling in response to specific stimuli. This review discusses the AMPK signaling associated with different subcellular compartments, including lysosomes, endoplasmic reticulum, mitochondria, Golgi apparatus, nucleus, and cell junctions. Because altered AMPK signaling is associated with various pathologic conditions including cancer, targeting AMPK signaling in different subcellular compartments may present attractive therapeutic approaches for treatment of disease.

When histones are under glucose starvation

Under nutritional stress, cells undergo metabolic rewiring that results in changes of various cellular processes that include gene transcription. This transcriptional regulation requires dynamic chromatin remodeling that involves histone post-translational modifications. There are several histone marks that may act as switches upon starvation for stress-response pathways.

Metabolic choreography of gene expression: nutrient transactions with the epigenome

Eukaryotic complexity and thus their ability to respond to diverse cues are largely driven by varying expression of gene products, qualitatively and quantitatively. Protein adducts in the form of post-translational modifications, most of which are derived from metabolic intermediates, allow fine tuning of gene expression at multiple levels. With the advent of high-throughput and high-resolution mapping technologies there has been an explosion in terms of the kind of modifications on chromatin and other factors that govern gene expression. Moreover, even the classical notion of acetylation and methylation dependent regulation of transcription is now known to be intrinsically coupled to biochemical pathways, which were otherwise regarded as 'mundane'. Here we have not only reviewed some of the recent literature but also have highlighted the dependence of gene regulatory mechanisms on metabolic inputs, both direct and indirect. We have also tried to bring forth some of the open questions, and how our understanding of gene expression has changed dramatically over the last few years, which has largely become metabolism centric. Finally, metabolic regulation of epigenome and gene expression has gained much traction due to the increased incidence of lifestyle and age-related diseases.

AMP-activated protein kinase links acetyl-CoA homeostasis to BRD4 recruitment in acute myeloid leukemia

Altered metabolism fuels 2 hallmark properties of cancer cells: unlimited proliferation and differentiation blockade. Adenosine monophosphate-activated protein kinase (AMPK) is a master regulator of bioenergetics crucial for glucose metabolism in acute myeloid leukemia (AML), and its inhibition delays leukemogenesis, but whether the metabolic function of AMPK alters the AML epigenome remains unknown. Here, we demonstrate that AMPK maintains the epigenome of MLL-rearranged AML by linking acetyl-coenzyme A (CoA) homeostasis to Bromodomain and Extra-Terminal domain (BET) protein recruitment to chromatin. AMPK deletion reduced acetyl-CoA and histone acetylation, displacing BET proteins from chromatin in leukemia-initiating cells. In both mouse and patient-derived xenograft AML models, treating with AMPK and BET inhibitors synergistically suppressed AML. Our results provide a therapeutic rationale to target AMPK and BET for AML therapy.

Fluctuations of Histone Chemical Modifications in Breast, Prostate, and Colorectal Cancer: An Implication of Phytochemicals as Defenders of Chromatin Equilibrium

Natural substances of plant origin exert health beneficiary efficacy due to the content of various phytochemicals. Significant anticancer abilities of natural compounds are mediated via various processes such as regulation of a cell's epigenome. The potential antineoplastic activity of plant natural substances mediated by their action on posttranslational histone modifications (PHMs) is currently a highly evaluated area of cancer research. PHMs play an important role in maintaining chromatin structure and regulating gene expression. Aberrations in PHMs are directly linked to the process of carcinogenesis in cancer such as breast (BC), prostate (PC), and colorectal (CRC) cancer, common malignant diseases in terms of incidence and mortality among both men and women. This review summarizes the effects of plant phytochemicals (isolated or mixtures) on cancer-associated PHMs (mainly modulation of acetylation and methylation) resulting in alterations of chromatin structure that are related to the regulation of transcription activity of specific oncogenes, which are crucial in the development of BC, PC, and CRC. Significant effectiveness of natural compounds in the modulation of aberrant PHMs were confirmed by a number of in vitro or in vivo studies in preclinical cancer research. However, evidence concerning PHMs-modulating abilities of plant-based natural substances in clinical trials is insufficient.

Epigenetic Regulation of miRNA Expression in Malignant Mesothelioma: miRNAs as Biomarkers of Early Diagnosis and Therapy

Asbestos exposure leads to epigenetic and epigenomic modifications that, in association with ROS-induced DNA damage, contribute to cancer onset. Few miRNAs epigenetically regulated in MM have been described in literature; miR-126, however, is one of them, and its expression is regulated by epigenetic mechanisms. Asbestos exposure induces early changes in the miRNAs, which are reversibly expressed as protective species, and their inability to reverse reflects the inability of the cells to restore the physiological miRNA levels despite the cessation of carcinogen exposure. Changes in miRNA expression, which results from genetic/epigenetic changes during tumor formation and evolution, can be detected in fluids and used as cancer biomarkers. This article has reviewed the epigenetic mechanisms involved in miRNA expression in MM, focusing on their role as biomarkers of early diagnosis and therapeutic effects.

p21cip1/waf1 Coordinate Autophagy, Proliferation and Apoptosis in Response to Metabolic Stress

Cancer cells possess metabolic properties that are different from benign cells. These unique characteristics have become attractive targets that are being actively investigated for cancer therapy. p21cip1/waf1, also known as Cyclin-Dependent Kinase inhibitor 1A, is encoded by the CDKN1A gene. It is a major p53 target gene involved in cell cycle progression that has been extensively evaluated. To date, p21 has been reported to regulate various cell functions, both dependent and independent of p53. Besides regulating the cell cycle, p21 also modulates apoptosis, induces senescence, and maintains cellular quiescence in response to various stimuli. p21 transcription is induced in response to stresses, including those from oxidative and chemotherapeutic treatment. A recent study has shown that in response to metabolic stresses such as nutrient and energy depletion, p21 expression is induced to regulate various cell functions. Despite the biological significance, the mechanism of p21 regulation in cancer adaptation to metabolic stress is underexplored and thus represents an exciting field. This review focuses on the recent development of p21 regulation in response to metabolic stress and its impact in inducing cell cycle arrest and death in cancer cells.

Negative regulation of AMPKα1 by PIM2 promotes aerobic glycolysis and tumorigenesis in endometrial cancer

Endometrial cancer (EC) is one of the most common gynecologic malignancies. However, the molecular mechanisms underlying the development and progression of EC remain unclear. Here, we demonstrated that the protein proviral insertion in murine lymphomas 2 (PIM2) was necessary for maintaining EC tumorigenesis in vivo and in vitro, and could inhibit AMPKα1 kinase activity in EC cells. Specifically, we found that PIM2 bound to AMPKα1, and directly phosphorylated it on Thr467. Phosphorylation of AMPKα1 by PIM2 led to decreasing AMPKα1 kinase activity, which in turn promoted aerobic glycolysis and tumor growth. In addition, PIM2 expression positively correlated with AMPKα1 Thr467 phosphorylation in EC tissues. Further, treatment with a combination of the PIM2 inhibitor SMI-4a and the AMPKα1 activator AICAR could effectively inhibit tumor growth. Thus, our findings provide insight into the role of PIM2 and AMPKα1 in EC and suggest that combination targeting of these proteins may represent a new strategy for EC treatment.

Nicotinamide Augments the Anti-Inflammatory Properties of Resveratrol through PARP1 Activation

Resveratrol (RSV) and nicotinamide (NAM) have garnered considerable attention due to their anti-inflammatory and anti-aging properties. NAM is a transient inhibitor of class III histone deacetylase SIRTs (silent mating type information regulation 2 homologs) and SIRT1 is an inhibitor of poly-ADP-ribose polymerase-1 (PARP1). The debate on the relationship between RSV and SIRT1 has precluded the use of RSV as a therapeutic drug. Recent work demonstrated that RSV facilitates tyrosyl-tRNA synthetase (TyrRS)-dependent activation of PARP1. Moreover, treatment with NAM is sufficient to facilitate the nuclear localization of TyrRS that activates PARP1. RSV and NAM have emerged as potent agonists of PARP1 through inhibition of SIRT1. In this study, we evaluated the effects of RSV and NAM on pro-inflammatory macrophages. Our results demonstrate that treatment with either RSV or NAM attenuates the expression of pro-inflammatory markers. Strikingly, the combination of RSV with NAM, exerts additive effects on PARP1 activation. Consistently, treatment with PARP1 inhibitor antagonized the anti-inflammatory effect of both RSV and NAM. For the first time, we report the ability of NAM to augment PARP1 activation, induced by RSV, and its associated anti-inflammatory effects mediated through the induction of BCL6 with the concomitant down regulation of COX-2.

Epigenetic Regulation at the Interplay Between Gut Microbiota and Host Metabolism

Gut microbiota communities have coevolved for millions of years in a symbiotic relationship with their mammalian hosts. Elucidating and understanding the molecular mechanisms by which microbiota interacts with its host and how this contributes to the homeostasis of the host is crucial. One of these molecular relationships is the so-called chemical crosstalk between microbiota and host metabolisms, including the poorly explored epigenetic regulation of host tissues by the metabolic activity of gut microbiota in response to changes in diet. DNA methylation and histone modifications are epigenetic marks partly regulated by enzymes such as methylases and acetylases, whose activity depend on host and microbiota metabolites that act as substrates and cofactors for these reactions. However, providing a complete mechanistic description of the regulatory interactions between both metabolisms and the impact on the expression of host genes through an epigenetic modulation, remains elusive. This article presents our perspective on how metabolomic, metagenomic, transcriptomic, and epigenomic data can be used to investigate the "microbiota-nutrient metabolism-epigenetics axis." We also discuss the implications and opportunities this knowledge may have for basic and applied science, such as the impact on the way we structure future research, understand, and prevent diseases like type 2 diabetes or obesity.

Critical role of AMPK in redox regulation under glucose starvation

Glucose starvation is one of the major forms of metabolic stress in cancer cells. Deprivation of glucose impairs glycolysis and the pentose phosphate pathway, which elicits oxidative stress due to enhanced production of reactive oxygen species (ROS) and impaired antioxidant system, leading to redox imbalance and cell death. Under glucose starvation, the 5' AMP-activated protein kinase (AMPK) plays a critical role in maintaining redox homeostasis and cell survival via multiple pathways, such as regulation of fatty acid metabolism and antioxidant response. Convergence of ROS and the glucose metabolic pathway reveals novel molecular targets for the development of effective cancer therapeutic strategies. Interestingly, AMPK, along with its upstream kinase liver kinase B1 (LKB1), has been regarded to play a tumor suppressor role. However, emerging studies have provided novel insights into the pro-tumor survival function of the LKB1-AMPK pathway. Therefore, targeting metabolic and oxidative stress in cancer cells, with manipulation of AMPK activity, is a promising strategy in developing novel cancer therapeutic agents.

The role of epigenetics in hypothalamic energy balance control: implications for obesity

Despite enormous social and scientific efforts, obesity rates continue to increase worldwide. While genetic factors contribute to obesity development, genetics alone cannot explain the current epidemic. Obesity is essentially the consequence of complex genetic-environmental interactions. Evidence suggests that contemporary lifestyles trigger epigenetic changes, which can dysregulate energy balance and thus contribute to obesity. The hypothalamus plays a pivotal role in the regulation of body weight, through a sophisticated network of neuronal systems. Alterations in the activity of these neuronal pathways have been implicated in the pathophysiology of obesity. Here, we review the current knowledge on the central control of energy balance with a focus on recent studies linking epigenetic mechanisms in the hypothalamus to the development of obesity and metabolic disorders.

AMPK regulates germline stem cell quiescence and integrity through an endogenous small RNA pathway

During suboptimal growth conditions, Caenorhabditis elegans larvae undergo a global developmental arrest called "dauer." During this stage, the germline stem cells (GSCs) become quiescent in an AMP-activated Protein Kinase (AMPK)-dependent manner, and in the absence of AMPK, the GSCs overproliferate and lose their reproductive capacity, leading to sterility when mutant animals resume normal growth. These defects correlate with the altered abundance and distribution of a number of chromatin modifications, all of which can be corrected by disabling components of the endogenous small RNA pathway, suggesting that AMPK regulates germ cell integrity by targeting an RNA interference (RNAi)-like pathway during dauer. The expression of AMPK in somatic cells restores all the germline defects, potentially through the transmission of small RNAs. Our findings place AMPK at a pivotal position linking energy stress detected in the soma to a consequent endogenous small RNA-mediated adaptation in germline gene expression, thereby challenging the "permeability" of the Weismann barrier.