Publications by authors named "Nika N Danial"

47 Publications

Glucose metabolism and pyruvate carboxylase enhance glutathione synthesis and restrict oxidative stress in pancreatic islets.

Cell Rep 2021 Nov;37(8):110037

Department of Cancer Biology, Dana-Farber Cancer Institute, 450 Brookline Ave., Boston, MA 02115, USA; Department of Medical Oncology, Dana-Farber Cancer Institute, Boston 02115, MA, USA; Department of Medicine, Harvard Medical School, 240 Longwood Ave., Boston, MA 02115, USA. Electronic address:

Glucose metabolism modulates the islet β cell responses to diabetogenic stress, including inflammation. Here, we probed the metabolic mechanisms that underlie the protective effect of glucose in inflammation by interrogating the metabolite profiles of primary islets from human donors and identified de novo glutathione synthesis as a prominent glucose-driven pro-survival pathway. We find that pyruvate carboxylase is required for glutathione synthesis in islets and promotes their antioxidant capacity to counter inflammation and nitrosative stress. Loss- and gain-of-function studies indicate that pyruvate carboxylase is necessary and sufficient to mediate the metabolic input from glucose into glutathione synthesis and the oxidative stress response. Altered redox metabolism and cellular capacity to replenish glutathione pools are relevant in multiple pathologies beyond obesity and diabetes. Our findings reveal a direct interplay between glucose metabolism and glutathione biosynthesis via pyruvate carboxylase. This metabolic axis may also have implications in other settings where sustaining glutathione is essential.
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http://dx.doi.org/10.1016/j.celrep.2021.110037DOI Listing
November 2021

BAD regulates mammary gland morphogenesis by 4E-BP1-mediated control of localized translation in mouse and human models.

Nat Commun 2021 05 19;12(1):2939. Epub 2021 May 19.

Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.

Elucidation of non-canonical protein functions can identify novel tissue homeostasis pathways. Herein, we describe a role for the Bcl-2 family member BAD in postnatal mammary gland morphogenesis. In Bad knock-in mice, where BAD cannot undergo phosphorylation at 3 key serine residues, pubertal gland development is delayed due to aberrant tubulogenesis of the ductal epithelium. Proteomic and RPPA analyses identify that BAD regulates focal adhesions and the mRNA translation repressor, 4E-BP1. These results suggest that BAD modulates localized translation that drives focal adhesion maturation and cell motility. Consistent with this, cells within Bad organoids contain unstable protrusions with decreased compartmentalized mRNA translation and focal adhesions, and exhibit reduced cell migration and tubulogenesis. Critically, protrusion stability is rescued by 4E-BP1 depletion. Together our results confirm an unexpected role of BAD in controlling localized translation and cell migration during mammary gland development.
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http://dx.doi.org/10.1038/s41467-021-23269-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8134504PMC
May 2021

UCP1 governs liver extracellular succinate and inflammatory pathogenesis.

Nat Metab 2021 05 17;3(5):604-617. Epub 2021 May 17.

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.

Non-alcoholic fatty liver disease (NAFLD), the most prevalent liver pathology worldwide, is intimately linked with obesity and type 2 diabetes. Liver inflammation is a hallmark of NAFLD and is thought to contribute to tissue fibrosis and disease pathogenesis. Uncoupling protein 1 (UCP1) is exclusively expressed in brown and beige adipocytes, and has been extensively studied for its capacity to elevate thermogenesis and reverse obesity. Here we identify an endocrine pathway regulated by UCP1 that antagonizes liver inflammation and pathology, independent of effects on obesity. We show that, without UCP1, brown and beige fat exhibit a diminished capacity to clear succinate from the circulation. Moreover, UCP1KO mice exhibit elevated extracellular succinate in liver tissue that drives inflammation through ligation of its cognate receptor succinate receptor 1 (SUCNR1) in liver-resident stellate cell and macrophage populations. Conversely, increasing brown and beige adipocyte content in mice antagonizes SUCNR1-dependent inflammatory signalling in the liver. We show that this UCP1-succinate-SUCNR1 axis is necessary to regulate liver immune cell infiltration and pathology, and systemic glucose intolerance in an obesogenic environment. As such, the therapeutic use of brown and beige adipocytes and UCP1 extends beyond thermogenesis and may be leveraged to antagonize NAFLD and SUCNR1-dependent liver inflammation.
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http://dx.doi.org/10.1038/s42255-021-00389-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8207988PMC
May 2021

Development of a novel fluorescent biosensor for dynamic monitoring of metabolic methionine redox status in cells and tissues.

Biosens Bioelectron 2021 Apr 29;178:113031. Epub 2021 Jan 29.

Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 02841, Republic of Korea. Electronic address:

Aberrant production of reactive oxygen species (ROS) leads to tissue damage accumulation, which is associated with a myriad of human pathologies. Although several sensors have been developed for ROS quantification, their applications for ROS-related human physiologies and pathologies still remain problematic due to the unstable nature of ROS. Herein, we developed Trx1-cpYFP-fRMsr (TYfR), a genetically-encoded fluorescent biosensor with the remarkable specificity and sensitivity toward fMetRO (free Methionine-R-sulfoxide), allowing for dynamic quantification of physiological levels of fMetRO, a novel indicator of ROS and methionine redox status in vitro and in vivo. Moreover, using the sensor, we observed a significant fMetRO enrichment in serum from patients with acute coronary syndrome, one of the most severe cardiovascular diseases, which becomes more evident following percutaneous coronary intervention. Collectively, this study proposes that fMetRO is a novel biomarker of tissue damage accumulation in ROS-associated human pathologies, and that TYfR is a promising tool for quantifying fMetRO with potentials in versatile applications.
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http://dx.doi.org/10.1016/j.bios.2021.113031DOI Listing
April 2021

CRISPR-engineered human brown-like adipocytes prevent diet-induced obesity and ameliorate metabolic syndrome in mice.

Sci Transl Med 2020 08;12(558)

Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA.

Brown and brown-like beige/brite adipocytes dissipate energy and have been proposed as therapeutic targets to combat metabolic disorders. However, the therapeutic effects of cell-based therapy in humans remain unclear. Here, we created human brown-like (HUMBLE) cells by engineering human white preadipocytes using CRISPR-Cas9-SAM-gRNA to activate endogenous uncoupling protein 1 expression. Obese mice that received HUMBLE cell transplants showed a sustained improvement in glucose tolerance and insulin sensitivity, as well as increased energy expenditure. Mechanistically, increased arginine/nitric oxide (NO) metabolism in HUMBLE adipocytes promoted the production of NO that was carried by -nitrosothiols and nitrite in red blood cells to activate endogenous brown fat and improved glucose homeostasis in recipient animals. Together, these data demonstrate the utility of using CRISPR-Cas9 technology to engineer human white adipocytes to display brown fat-like phenotypes and may open up cell-based therapeutic opportunities to combat obesity and diabetes.
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http://dx.doi.org/10.1126/scitranslmed.aaz8664DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7704293PMC
August 2020

Glucose-dependent partitioning of arginine to the urea cycle protects β-cells from inflammation.

Nat Metab 2020 05 11;2(5):432-446. Epub 2020 May 11.

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA.

Chronic inflammation is linked to diverse disease processes, but the intrinsic mechanisms that determine cellular sensitivity to inflammation are incompletely understood. Here, we show the contribution of glucose metabolism to inflammation-induced changes in the survival of pancreatic islet β-cells. Using metabolomic, biochemical and functional analyses, we investigate the protective versus non-protective effects of glucose in the presence of pro-inflammatory cytokines. When protective, glucose metabolism augments anaplerotic input into the TCA cycle via pyruvate carboxylase (PC) activity, leading to increased aspartate levels. This metabolic mechanism supports the argininosuccinate shunt, which fuels ureagenesis from arginine and conversely diminishes arginine utilization for production of nitric oxide (NO), a chief mediator of inflammatory cytotoxicity. Activation of the PC-urea cycle axis is sufficient to suppress NO synthesis and shield cells from death in the context of inflammation and other stress paradigms. Overall, these studies uncover a previously unappreciated link between glucose metabolism and arginine-utilizing pathways via PC-directed ureagenesis as a protective mechanism.
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http://dx.doi.org/10.1038/s42255-020-0199-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7568475PMC
May 2020

Hydrocarbon-Stitched Peptide Agonists of Glucagon-Like Peptide-1 Receptor.

ACS Chem Biol 2020 06 27;15(6):1340-1348. Epub 2020 May 27.

Department of Pediatric Oncology, Dana-Farber Cancer Institute, 450 Brookline Avenue, Boston, Massachusetts 02215, United States.

Glucagon-like peptide 1 (GLP-1) is a natural peptide agonist of the GLP-1 receptor (GLP-1R) found on pancreatic β-cells. Engagement of the receptor stimulates insulin release in a glucose-dependent fashion and increases β-cell mass, two ideal features for pharmacologic management of type 2 diabetes. Thus, intensive efforts have focused on developing GLP-1-based peptide agonists of GLP-1R for therapeutic application. A primary challenge has been the naturally short half-life of GLP-1 due to its rapid proteolytic degradation . Whereas mutagenesis and lipidation strategies have yielded clinical agents, we developed an alternative approach to preserving the structure and function of GLP-1 by all-hydrocarbon , + 7 stitching. This particular "stitch" is especially well-suited for reinforcing and protecting the structural fidelity of GLP-1. Lead constructs demonstrate striking proteolytic stability and potent biological activity . Thus, we report a facile approach to generating alternative GLP-1R agonists for glycemic control.
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http://dx.doi.org/10.1021/acschembio.0c00308DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7366314PMC
June 2020

Partitioning of MLX-Family Transcription Factors to Lipid Droplets Regulates Metabolic Gene Expression.

Mol Cell 2020 03 4;77(6):1251-1264.e9. Epub 2020 Feb 4.

Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA; Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA. Electronic address:

Lipid droplets (LDs) store lipids for energy and are central to cellular lipid homeostasis. The mechanisms coordinating lipid storage in LDs with cellular metabolism are unclear but relevant to obesity-related diseases. Here we utilized genome-wide screening to identify genes that modulate lipid storage in macrophages, a cell type involved in metabolic diseases. Among ∼550 identified screen hits is MLX, a basic helix-loop-helix leucine-zipper transcription factor that regulates metabolic processes. We show that MLX and glucose-sensing family members MLXIP/MondoA and MLXIPL/ChREBP bind LDs via C-terminal amphipathic helices. When LDs accumulate in cells, these transcription factors bind to LDs, reducing their availability for transcriptional activity and attenuating the response to glucose. Conversely, the absence of LDs results in hyperactivation of MLX target genes. Our findings uncover a paradigm for a lipid storage response in which binding of MLX transcription factors to LD surfaces adjusts the expression of metabolic genes to lipid storage levels.
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http://dx.doi.org/10.1016/j.molcel.2020.01.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7397554PMC
March 2020

Fibroblastic reticular cells enhance T cell metabolism and survival via epigenetic remodeling.

Nat Immunol 2019 12 21;20(12):1668-1680. Epub 2019 Oct 21.

Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA, USA.

Lymph node fibroblastic reticular cells (FRCs) respond to signals from activated T cells by releasing nitric oxide, which inhibits T cell proliferation and restricts the size of the expanding T cell pool. Whether interactions with FRCs also support the function or differentiation of activated CD8 T cells is not known. Here we report that encounters with FRCs enhanced cytokine production and remodeled chromatin accessibility in newly activated CD8 T cells via interleukin-6. These epigenetic changes facilitated metabolic reprogramming and amplified the activity of pro-survival pathways through differential transcription factor activity. Accordingly, FRC conditioning significantly enhanced the persistence of virus-specific CD8 T cells in vivo and augmented their differentiation into tissue-resident memory T cells. Our study demonstrates that FRCs play a role beyond restricting T cell expansion-they can also shape the fate and function of CD8 T cells.
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http://dx.doi.org/10.1038/s41590-019-0515-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7464610PMC
December 2019

HCF-1 Regulates De Novo Lipogenesis through a Nutrient-Sensitive Complex with ChREBP.

Mol Cell 2019 07 18;75(2):357-371.e7. Epub 2019 Jun 18.

Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02215, USA; Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA; Department of Medicine, Harvard Medical School, Boston, MA 02115, USA. Electronic address:

Carbohydrate response element binding protein (ChREBP) is a key transcriptional regulator of de novo lipogenesis (DNL) in response to carbohydrates and in hepatic steatosis. Mechanisms underlying nutrient modulation of ChREBP are under active investigation. Here we identify host cell factor 1 (HCF-1) as a previously unknown ChREBP-interacting protein that is enriched in liver biopsies of nonalcoholic steatohepatitis (NASH) patients. Biochemical and genetic studies show that HCF-1 is O-GlcNAcylated in response to glucose as a prerequisite for its binding to ChREBP and subsequent recruitment of OGT, ChREBP O-GlcNAcylation, and activation. The HCF-1:ChREBP complex resides at lipogenic gene promoters, where HCF-1 regulates H3K4 trimethylation to prime recruitment of the Jumonji C domain-containing histone demethylase PHF2 for epigenetic activation of these promoters. Overall, these findings define HCF-1's interaction with ChREBP as a previously unappreciated mechanism whereby glucose signals are both relayed to ChREBP and transmitted for epigenetic regulation of lipogenic genes.
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http://dx.doi.org/10.1016/j.molcel.2019.05.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6744259PMC
July 2019

Grasping for aspartate in tumour metabolism.

Nat Cell Biol 2018 07;20(7):738-739

Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA.

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http://dx.doi.org/10.1038/s41556-018-0137-9DOI Listing
July 2018

BAD and K channels regulate neuron excitability and epileptiform activity.

Elife 2018 01 25;7. Epub 2018 Jan 25.

Department of Neurobiology, Harvard Medical School, Boston, United States.

Brain metabolism can profoundly influence neuronal excitability. Mice with genetic deletion or alteration of (CL-2 gonist of cell eath) exhibit altered brain-cell fuel metabolism, accompanied by resistance to acutely induced epileptic seizures; this seizure protection is mediated by ATP-sensitive potassium (K) channels. Here we investigated the effect of BAD manipulation on K channel activity and excitability in acute brain slices. We found that BAD's influence on neuronal K channels was cell-autonomous and directly affected dentate granule neuron (DGN) excitability. To investigate the role of neuronal K channels in the anticonvulsant effects of BAD, we imaged calcium during picrotoxin-induced epileptiform activity in entorhinal-hippocampal slices. BAD knockout reduced epileptiform activity, and this effect was lost upon knockout or pharmacological inhibition of K channels. Targeted BAD knockout in DGNs alone was sufficient for the antiseizure effect in slices, consistent with a 'dentate gate' function that is reinforced by increased K channel activity.
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http://dx.doi.org/10.7554/eLife.32721DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5785210PMC
January 2018

BAD knockout provides metabolic seizure resistance in a genetic model of epilepsy with sudden unexplained death in epilepsy.

Epilepsia 2018 01 23;59(1):e1-e4. Epub 2017 Nov 23.

Department of Neurobiology, Harvard Medical School, Boston, MA, USA.

Metabolic alteration, either through the ketogenic diet (KD) or by genetic alteration of the BAD protein, can produce seizure protection in acute chemoconvulsant models of epilepsy. To assess the seizure-protective role of knocking out (KO) the Bad gene in a chronic epilepsy model, we used the Kcna1 model of epilepsy, which displays progressively increased seizure severity and recapitulates the early death seen in sudden unexplained death in epilepsy (SUDEP). Beginning on postnatal day 24 (P24), we continuously video monitored Kcna1 and Kcna1 Bad double knockout mice to assess survival and seizure severity. We found that Kcna1 Bad mice outlived Kcna1 mice by approximately 2 weeks. Kcna1 Bad mice also spent significantly less time in seizure than Kcna1 mice on P24 and the day of death, showing that BadKO provides seizure resistance in a genetic model of chronic epilepsy.
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http://dx.doi.org/10.1111/epi.13960DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5760331PMC
January 2018

Differential contribution of the mitochondrial translation pathway to the survival of diffuse large B-cell lymphoma subsets.

Cell Death Differ 2017 02 21;24(2):251-262. Epub 2016 Oct 21.

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.

Diffuse large B-cell lymphomas (DLBCLs) are a highly heterogeneous group of tumors in which subsets share molecular features revealed by gene expression profiles and metabolic fingerprints. While B-cell receptor (BCR)-dependent DLBCLs are glycolytic, OxPhos-DLBCLs rely on mitochondrial energy transduction and nutrient utilization pathways that provide pro-survival benefits independent of BCR signaling. Integral to these metabolic distinctions is elevated mitochondrial electron transport chain (ETC) activity in OxPhos-DLBCLs compared with BCR-DLBCLs, which is linked to greater protein abundance of ETC components. To gain insights into molecular determinants of the selective increase in ETC activity and dependence on mitochondrial energy metabolism in OxPhos-DLBCLs, we examined the mitochondrial translation pathway in charge of the synthesis of mitochondrial DNA encoded ETC subunits. Quantitative mass spectrometry identified increased expression of mitochondrial translation factors in OxPhos-DLBCL as compared with the BCR subtype. Biochemical and functional assays indicate that the mitochondrial translation pathway is required for increased ETC activity and mitochondrial energy reserves in OxPhos-DLBCL. Importantly, molecular depletion of several mitochondrial translation proteins using RNA interference or pharmacological perturbation of the mitochondrial translation pathway with the FDA-approved inhibitor tigecycline (Tigecyl) is selectively toxic to OxPhos-DLBCL cell lines and primary tumors. These findings provide additional molecular insights into the metabolic characteristics of OxPhos-DLBCLs, and mark the mitochondrial translation pathway as a potential therapeutic target in these tumors.
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http://dx.doi.org/10.1038/cdd.2016.116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5299709PMC
February 2017

Regulation of mitochondrial nutrient and energy metabolism by BCL-2 family proteins.

Trends Endocrinol Metab 2015 Apr 5;26(4):165-75. Epub 2015 Mar 5.

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA. Electronic address:

Cells have evolved a highly integrated network of mechanisms to coordinate cellular survival/death, proliferation, differentiation, and repair with metabolic states. It is therefore not surprising that proteins with canonical roles in cell death/survival also modulate nutrient and energy metabolism and vice versa. The finding that many BCL-2 (B cell lymphoma 2) proteins reside at mitochondria or can translocate to this organelle has long motivated investigation into their involvement in normal mitochondrial physiology and metabolism. These endeavors have led to the discovery of homeostatic roles for BCL-2 proteins beyond apoptosis. We predominantly focus on recent findings that link select BCL-2 proteins to carbon substrate utilization at the level of mitochondrial fuel choice, electron transport, and metabolite import independent of their cell death regulatory function.
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http://dx.doi.org/10.1016/j.tem.2015.02.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4380665PMC
April 2015

Phospho-BAD BH3 mimicry protects β cells and restores functional β cell mass in diabetes.

Cell Rep 2015 Feb 29;10(4):497-504. Epub 2015 Jan 29.

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA. Electronic address:

Strategies that simultaneously enhance the survival and glucose responsiveness of insulin-producing β cells will greatly augment β cell replacement therapies in type 1 diabetes (T1D). We show that genetic and pharmacologic mimetics of the phosphorylated BCL-2 homology 3 (BH3) domain of BAD impart β-cell-autonomous protective effects in the face of stress stimuli relevant to β cell demise in T1D. Importantly, these benefits translate into improved engraftment of donor islets in transplanted diabetic mice, increased β cell viability in islet grafts, restoration of insulin release, and diabetes reversal. Survival of β cells in this setting is not merely due to the inability of phospho-BAD to suppress prosurvival BCL-2 proteins but requires its activation of the glucose-metabolizing enzyme glucokinase. Thus, BAD phospho-BH3 mimetics may prove useful in the restoration of functional β cell mass in diabetes.
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http://dx.doi.org/10.1016/j.celrep.2014.12.056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4991214PMC
February 2015

Measurement of mitochondrial oxygen consumption rates in mouse primary neurons and astrocytes.

Methods Mol Biol 2015 ;1241:59-69

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, 02115, USA.

The introduction of microplate-based assays that measure extracellular fluxes in intact, living cells has revolutionized the field of cellular bioenergetics. Here, we describe a method for real time assessment of mitochondrial oxygen consumption rates in primary mouse cortical neurons and astrocytes. This method requires the Extracellular Flux Analyzer Instrument (XF24, Seahorse Biosciences), which uses fluorescent oxygen sensors in a microplate assay format.
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http://dx.doi.org/10.1007/978-1-4939-1875-1_6DOI Listing
June 2015

Adipsin is an adipokine that improves β cell function in diabetes.

Cell 2014 Jul;158(1):41-53

Dana-Farber Cancer Institute and the Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA. Electronic address:

A hallmark of type 2 diabetes mellitus (T2DM) is the development of pancreatic β cell failure, which results in insulinopenia and hyperglycemia. We show that the adipokine adipsin has a beneficial role in maintaining β cell function. Animals genetically lacking adipsin have glucose intolerance due to insulinopenia; isolated islets from these mice have reduced glucose-stimulated insulin secretion. Replenishment of adipsin to diabetic mice treated hyperglycemia by boosting insulin secretion. We identify C3a, a peptide generated by adipsin, as a potent insulin secretagogue and show that the C3a receptor is required for these beneficial effects of adipsin. C3a acts on islets by augmenting ATP levels, respiration, and cytosolic free Ca(2+). Finally, we demonstrate that T2DM patients with β cell failure are deficient in adipsin. These findings indicate that the adipsin/C3a pathway connects adipocyte function to β cell physiology, and manipulation of this molecular switch may serve as a therapy in T2DM.
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http://dx.doi.org/10.1016/j.cell.2014.06.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4128197PMC
July 2014

Inhibiting Tankyrases sensitizes KRAS-mutant cancer cells to MEK inhibitors via FGFR2 feedback signaling.

Cancer Res 2014 Jun 18;74(12):3294-305. Epub 2014 Apr 18.

Authors' Affiliations: Oncology Department, Novartis Institutes for BioMedical Research; Zalicus Inc., Cambridge; and Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts

Tankyrases (TNKS) play roles in Wnt signaling, telomere homeostasis, and mitosis, offering attractive targets for anticancer treatment. Using unbiased combination screening in a large panel of cancer cell lines, we have identified a strong synergy between TNKS and MEK inhibitors (MEKi) in KRAS-mutant cancer cells. Our study uncovers a novel function of TNKS in the relief of a feedback loop induced by MEK inhibition on FGFR2 signaling pathway. Moreover, dual inhibition of TNKS and MEK leads to more robust apoptosis and antitumor activity both in vitro and in vivo than effects observed by previously reported MEKi combinations. Altogether, our results show how a novel combination of TNKS and MEK inhibitors can be highly effective in targeting KRAS-mutant cancers by suppressing a newly discovered resistance mechanism.
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http://dx.doi.org/10.1158/0008-5472.CAN-14-0138-TDOI Listing
June 2014

D-2-hydroxyglutarate produced by mutant IDH2 causes cardiomyopathy and neurodegeneration in mice.

Genes Dev 2014 Mar;28(5):479-90

Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA;

Mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) have been discovered in several cancer types and cause the neurometabolic syndrome D2-hydroxyglutaric aciduria (D2HGA). The mutant enzymes exhibit neomorphic activity resulting in production of D2-hydroxyglutaric acid (D-2HG). To study the pathophysiological consequences of the accumulation of D-2HG, we generated transgenic mice with conditionally activated IDH2(R140Q) and IDH2(R172K) alleles. Global induction of mutant IDH2 expression in adults resulted in dilated cardiomyopathy, white matter abnormalities throughout the central nervous system (CNS), and muscular dystrophy. Embryonic activation of mutant IDH2 resulted in more pronounced phenotypes, including runting, hydrocephalus, and shortened life span, recapitulating the abnormalities observed in D2HGA patients. The diseased hearts exhibited mitochondrial damage and glycogen accumulation with a concordant up-regulation of genes involved in glycogen biosynthesis. Notably, mild cardiac hypertrophy was also observed in nude mice implanted with IDH2(R140Q)-expressing xenografts, suggesting that 2HG may potentially act in a paracrine fashion. Finally, we show that silencing of IDH2(R140Q) in mice with an inducible transgene restores heart function by lowering 2HG levels. Together, these findings indicate that inhibitors of mutant IDH2 may be beneficial in the treatment of D2HGA and suggest that 2HG produced by IDH mutant tumors has the potential to provoke a paraneoplastic condition.
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http://dx.doi.org/10.1101/gad.231233.113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3950345PMC
March 2014

Regulation of hepatic energy metabolism and gluconeogenesis by BAD.

Cell Metab 2014 Feb;19(2):272-84

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA. Electronic address:

The homeostatic balance of hepatic glucose utilization, storage, and production is exquisitely controlled by hormonal signals and hepatic carbon metabolism during fed and fasted states. How the liver senses extracellular glucose to cue glucose utilization versus production is not fully understood. We show that the physiologic balance of hepatic glycolysis and gluconeogenesis is regulated by Bcl-2-associated agonist of cell death (BAD), a protein with roles in apoptosis and metabolism. BAD deficiency reprograms hepatic substrate and energy metabolism toward diminished glycolysis, excess fatty acid oxidation, and exaggerated glucose production that escapes suppression by insulin. Genetic and biochemical evidence suggests that BAD's suppression of gluconeogenesis is actuated by phosphorylation of its BCL-2 homology (BH)-3 domain and subsequent activation of glucokinase. The physiologic relevance of these findings is evident from the ability of a BAD phosphomimic variant to counteract unrestrained gluconeogenesis and improve glycemia in leptin-resistant and high-fat diet models of diabetes and insulin resistance.
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http://dx.doi.org/10.1016/j.cmet.2013.12.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3971904PMC
February 2014

A phospho-BAD BH3 helix activates glucokinase by a mechanism distinct from that of allosteric activators.

Nat Struct Mol Biol 2014 Jan 8;21(1):36-42. Epub 2013 Dec 8.

1] Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA. [2] Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA.

Glucokinase (GK) is a glucose-phosphorylating enzyme that regulates insulin release and hepatic metabolism, and its loss of function is implicated in diabetes pathogenesis. GK activators (GKAs) are attractive therapeutics in diabetes; however, clinical data indicate that their benefits can be offset by hypoglycemia, owing to marked allosteric enhancement of the enzyme's glucose affinity. We show that a phosphomimetic of the BCL-2 homology 3 (BH3) α-helix derived from human BAD, a GK-binding partner, increases the enzyme catalytic rate without dramatically changing glucose affinity, thus providing a new mechanism for pharmacologic activation of GK. Remarkably, BAD BH3 phosphomimetic mediates these effects by engaging a new region near the enzyme's active site. This interaction increases insulin secretion in human islets and restores the function of naturally occurring human GK mutants at the active site. Thus, BAD phosphomimetics may serve as a new class of GKAs.
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http://dx.doi.org/10.1038/nsmb.2717DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4084830PMC
January 2014

Changing appetites: the adaptive advantages of fuel choice.

Trends Cell Biol 2014 Feb 7;24(2):118-27. Epub 2013 Sep 7.

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA. Electronic address:

Cells are capable of metabolizing a variety of carbon substrates, including glucose, fatty acids, ketone bodies, and amino acids. Cellular fuel choice not only fulfills specific biosynthetic needs, but also enables programmatic adaptations to stress conditions beyond compensating for changes in nutrient availability. Emerging evidence indicates that specific switches from utilization of one substrate to another can have protective or permissive roles in disease pathogenesis. Understanding the molecular determinants of cellular fuel preference may provide insights into the homeostatic control of stress responses, and unveil therapeutic targets. Here, we highlight overarching themes encompassing cellular fuel choice; its link to cell fate and function; its advantages in stress protection; and its contribution to metabolic dependencies and maladaptations in pathological conditions.
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http://dx.doi.org/10.1016/j.tcb.2013.07.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3946676PMC
February 2014

How does the ketogenic diet work? Four potential mechanisms.

J Child Neurol 2013 Aug 13;28(8):1027-33. Epub 2013 May 13.

Department of Cancer Biology, Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, MA, USA.

The ketogenic diet and its newer variants are clinically useful in treating epilepsy. They can also have antiepileptogenic properties and can eventually have a role in treating other neurologic and nonneurologic conditions. Despite being nearly a century old, identifying the molecular underpinnings of the ketogenic diet has been challenging. However, recent studies provide experimental evidence for 4 distinct mechanisms that could contribute to the antiseizure and other beneficial effects of these diets. These mechanisms include carbohydrate reduction, activation of adenosine triphosphate (ATP)-sensitive potassium channels by mitochondrial metabolism, inhibition of the mammalian target of rapamycin pathway, and inhibition of glutamatergic excitatory synaptic transmission.
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http://dx.doi.org/10.1177/0883073813487598DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3971996PMC
August 2013

Inactivation of BAD by IKK inhibits TNFα-induced apoptosis independently of NF-κB activation.

Cell 2013 Jan;152(1-2):304-15

Ben May Department for Cancer Research, The University of Chicago, Chicago, IL 60637, USA.

The IκB kinase complex (IKK) is a key regulator of immune responses, inflammation, cell survival, and tumorigenesis. The prosurvival function of IKK centers on activation of the transcription factor NF-κB, whose target gene products inhibit caspases and prevent prolonged JNK activation. Here, we report that inactivation of the BH3-only protein BAD by IKK independently of NF-κB activation suppresses TNFα-induced apoptosis. TNFα-treated Ikkβ(-/-) mouse embryonic fibroblasts (MEFs) undergo apoptosis significantly faster than MEFs deficient in both RelA and cRel due to lack of inhibition of BAD by IKK. IKK phosphorylates BAD at serine-26 (Ser26) and primes it for inactivation. Elimination of Ser26 phosphorylation promotes BAD proapoptotic activity, thereby accelerating TNFα-induced apoptosis in cultured cells and increasing mortality in animals. Our results reveal that IKK inhibits TNFα-induced apoptosis through two distinct but cooperative mechanisms: activation of the survival factor NF-κB and inactivation of the proapoptotic BH3-only BAD protein.
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http://dx.doi.org/10.1016/j.cell.2012.12.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3586589PMC
January 2013

Mitochondrial Atpif1 regulates haem synthesis in developing erythroblasts.

Nature 2012 Nov 7;491(7425):608-12. Epub 2012 Nov 7.

Department of Medicine, Division of Hematology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.

Defects in the availability of haem substrates or the catalytic activity of the terminal enzyme in haem biosynthesis, ferrochelatase (Fech), impair haem synthesis and thus cause human congenital anaemias. The interdependent functions of regulators of mitochondrial homeostasis and enzymes responsible for haem synthesis are largely unknown. To investigate this we used zebrafish genetic screens and cloned mitochondrial ATPase inhibitory factor 1 (atpif1) from a zebrafish mutant with profound anaemia, pinotage (pnt (tq209)). Here we describe a direct mechanism establishing that Atpif1 regulates the catalytic efficiency of vertebrate Fech to synthesize haem. The loss of Atpif1 impairs haemoglobin synthesis in zebrafish, mouse and human haematopoietic models as a consequence of diminished Fech activity and elevated mitochondrial pH. To understand the relationship between mitochondrial pH, redox potential, [2Fe-2S] clusters and Fech activity, we used genetic complementation studies of Fech constructs with or without [2Fe-2S] clusters in pnt, as well as pharmacological agents modulating mitochondrial pH and redox potential. The presence of [2Fe-2S] cluster renders vertebrate Fech vulnerable to perturbations in Atpif1-regulated mitochondrial pH and redox potential. Therefore, Atpif1 deficiency reduces the efficiency of vertebrate Fech to synthesize haem, resulting in anaemia. The identification of mitochondrial Atpif1 as a regulator of haem synthesis advances our understanding of the mechanisms regulating mitochondrial haem homeostasis and red blood cell development. An ATPIF1 deficiency may contribute to important human diseases, such as congenital sideroblastic anaemias and mitochondriopathies.
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http://dx.doi.org/10.1038/nature11536DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3504625PMC
November 2012

Metabolic signatures uncover distinct targets in molecular subsets of diffuse large B cell lymphoma.

Cancer Cell 2012 Oct;22(4):547-60

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.

Molecular signatures have identified several subsets of diffuse large B cell lymphoma (DLBCL) and rational targets within the B cell receptor (BCR) signaling axis. The OxPhos-DLBCL subset, which harbors the signature of genes involved in mitochondrial metabolism, is insensitive to inhibition of BCR survival signaling but is functionally undefined. We show that, compared with BCR-DLBCLs, OxPhos-DLBCLs display enhanced mitochondrial energy transduction, greater incorporation of nutrient-derived carbons into the tricarboxylic acid cycle, and increased glutathione levels. Moreover, perturbation of the fatty acid oxidation program and glutathione synthesis proved selectively toxic to this tumor subset. Our analysis provides evidence for distinct metabolic fingerprints and associated survival mechanisms in DLBCL and may have therapeutic implications.
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http://dx.doi.org/10.1016/j.ccr.2012.08.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3479446PMC
October 2012

Control of tumor bioenergetics and survival stress signaling by mitochondrial HSP90s.

Cancer Cell 2012 Sep;22(3):331-44

Prostate Cancer Discovery and Development Program, The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA.

Tumors successfully adapt to constantly changing intra- and extracellular environments, but the wirings of this process are still largely elusive. Here, we show that heat-shock-protein-90-directed protein folding in mitochondria, but not cytosol, maintains energy production in tumor cells. Interference with this process activates a signaling network that involves phosphorylation of nutrient-sensing AMP-activated kinase, inhibition of rapamycin-sensitive mTOR complex 1, induction of autophagy, and expression of an endoplasmic reticulum unfolded protein response. This signaling network confers a survival and proliferative advantage to genetically disparate tumors, and correlates with worse outcome in lung cancer patients. Therefore, mitochondrial heat shock protein 90s are adaptive regulators of tumor bioenergetics and tractable targets for cancer therapy.
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http://dx.doi.org/10.1016/j.ccr.2012.07.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3615709PMC
September 2012

Polysome profiling in liver identifies dynamic regulation of endoplasmic reticulum translatome by obesity and fasting.

PLoS Genet 2012 Aug 23;8(8):e1002902. Epub 2012 Aug 23.

Department of Genetics and Complex Diseases, Harvard School of Public Health, Boston, Massachusetts, USA.

Obesity-associated metabolic complications are generally considered to emerge from abnormalities in carbohydrate and lipid metabolism, whereas the status of protein metabolism is not well studied. Here, we performed comparative polysome and associated transcriptional profiling analyses to study the dynamics and functional implications of endoplasmic reticulum (ER)-associated protein synthesis in the mouse liver under conditions of obesity and nutrient deprivation. We discovered that ER from livers of obese mice exhibits a general reduction in protein synthesis, and comprehensive analysis of polysome-bound transcripts revealed extensive down-regulation of protein synthesis machinery, mitochondrial components, and bile acid metabolism in the obese translatome. Nutrient availability also plays an important but distinct role in remodeling the hepatic ER translatome in lean and obese mice. Fasting in obese mice partially reversed the overall translatomic differences between lean and obese nonfasted controls, whereas fasting of the lean mice mimicked many of the translatomic changes induced by the development of obesity. The strongest examples of such regulations were the reduction in Cyp7b1 and Slco1a1, molecules involved in bile acid metabolism. Exogenous expression of either gene significantly lowered plasma glucose levels, improved hepatic steatosis, but also caused cholestasis, indicating the fine balance bile acids play in regulating metabolism and health. Together, our work defines dynamic regulation of the liver translatome by obesity and nutrient availability, and it identifies a novel role for bile acid metabolism in the pathogenesis of metabolic abnormalities associated with obesity.
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http://dx.doi.org/10.1371/journal.pgen.1002902DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3426552PMC
August 2012

BAD-dependent regulation of fuel metabolism and K(ATP) channel activity confers resistance to epileptic seizures.

Neuron 2012 May;74(4):719-30

Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA.

Neuronal excitation can be substantially modulated by alterations in metabolism, as evident from the anticonvulsant effect of diets that reduce glucose utilization and promote ketone body metabolism. We provide genetic evidence that BAD, a protein with dual functions in apoptosis and glucose metabolism, imparts reciprocal effects on metabolism of glucose and ketone bodies in brain cells. These effects involve phosphoregulation of BAD and are independent of its apoptotic function. BAD modifications that reduce glucose metabolism produce a marked increase in the activity of metabolically sensitive K(ATP) channels in neurons, as well as resistance to behavioral and electrographic seizures in vivo. Seizure resistance is reversed by genetic ablation of the K(ATP) channel, implicating the BAD-K(ATP) axis in metabolic control of neuronal excitation and seizure responses.
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http://dx.doi.org/10.1016/j.neuron.2012.03.032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3361694PMC
May 2012
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