CHAPTERTHREEGeneDisruptionCausesMetabolicallyHealthyEpigeneticandChrom - PDF document

CHAPTERTHREEGeneDisruptionCausesMetabolicallyHealthyEpigeneticandChromatin-BasedMechanismsthatUncoupleObesityfromType2DiabetesFangnianWang,JudeT.Deeney,GeraldV.DenisIQuumInc,Marlborough,MA01752,USADepartmentofMedicine,BostonUniversitySchoolofMedicine,Boston,Massachusetts,USAFlowCytometryCoreFacility,BostonUniversitySchoolofMedicine,Boston,Massachusetts,USANutritionObesityResearchCenter,BostonUniversitySchoolofMedicine,Boston,Massachusetts,USACancerResearchCenter,BostonUniversitySchoolofMedicine,Boston,Massachusetts,USADepartmentofPharmacologyandExperimentalTherapeutics,BostonUniversitySchoolofMedicine,Boston,Massachusetts,USACorrespondingauthor:e-mailaddress:gdenis@bu.eduIntroduction:TheProblemofObesityandItsComplicationsComplexPolygenicInteractionswiththeEnvironmentandEpigeneticsinObesity52brd2loMouseModelofMetabolicallyHealthyObesity57GenetargetingofthelocusinmiceSystemic,protectivephenotypesinbrd2lobrd2lophenotypeprotectsadiposetissueInsulinresistantobesityisaninflammatorydiseaseMetabolicallyprotectivephenotypesinthebrd2loimmunesystem60WhoareMetabolicallyHealthyObeseHumans?OtherAnimalModelsofMetabolicallyHealthyDerepressionofInsulinTranscriptioninthebrd2loTranslationalImplicationsofEpigeneticReprogramming:ConclusionsDisturbedbodyenergybalancecanleadtoobesityandobesity-drivendiseasessuchasType2diabetes,whichhavereachedanepidemiclevel.Evidenceindicatesthatobesity-inducedinflammationisamajorcauseofinsulinresistanceandType2diabetes.Envi-ronmentalfactors,suchasnutrients,affectbodyenergybalancethroughepigeneticorchromatin-basedmechanisms.AsabromodomainandexternaldomainfamilyVitaminsandHormones,Volume912013ElsevierInc.ISSN0083-6729Allrightsreserved.http://dx.doi.org/10.1016/B978-0-12-407766-9.00003-1 Author's personal copy transcriptionregulator,Brd2regulatesexpressionofmanygenesthroughinterpretationofchromatincodesandparticipatesintheregulationofbodyenergybalanceandimmunefunction.Intheseverelyobesestate,Brd2knockdowninmicepreventedobesity-inducedinflammatoryresponses,protectedanimalsfrominsulinresistance,glucoseintoleranceandpancreaticbetacelldysfunction,andthusuncoupledobesityfromdiabetes.Brd2providesanimportantmodelforinvestigationofthefunctionoftranscriptionregulatorsandthedevelopmentofobesityanddiabetes;italsoprovidesapossible,innovativetargettotreatobesityanddiabetesthroughmodulationofthefunctionofachromatincodereader.ABBREVIATIONSbromodomainandextraterminaldomainbodymassindexhomeostaticmetabolicassessmentmajorhistocompatibilitycomplexperoxisomeproliferator-activatedreceptorsinglenucleotidepolymorphismstumornecrosisfactorTNF-relatedweakinducerofapoptosis 1.INTRODUCTION:THEPROBLEMOFOBESITYANDITSCOMPLICATIONSOverthecourseofrecordedhistory,manydifferentdiseasesandriskshavethreatenedhumansurvivalonawidescale,includingepidemicsofin-fectiousorganisms,war,starvation,famine,suddenclimatechange,andeth-niccleansing.AsrecentlyastheendoftheSecondWorldWar,achroniclackofcaloriesinEuropeandJapanwaswidelyacknowledgedasamajorcontributortopoorhealth,elevatedinfantmortality,increaseddiseasesus-ceptibility(particularlytotuberculosis),anditsattendantconsequencesofeconomicandpoliticalinstability.Theendofthatwarbroughtthebenefitsofmodernpeace:adramatictransformationoftheinternationaleconomy,accompaniedbyhugeincreasesinindustrialandagriculturaloutput,vastin-ternationaltradeinmanufacturedgoods,rawmaterialsandfoods(bothprocessedandunprocessed),andapronouncedshiftfrommanualtoseden-tarylabor.Thesetremendousstructuralandeconomicchanges,combinedwithincreasedlifeexpectancyandtheriseofagribusiness,advertising,andahugelysuccessfulinternationalfoodindustry,havecontributedtothetransformationofobesityfromaquaintfeatureofroyalfamiliesinformer FangnianWangetal. timestoanalarming,internationalpublichealthworrythataffectsallsocio-economicclassesatpresent.Thus,oftheseriousandwidespreadmenacestopublichealthinhumanhistory,obesityisthenewestchallenge.Obesityisdefinedasabodymassindex(BMI)of30,calculatedasbodyweightinkilogramsdividedbythesquareofheightincentimeters.Leanin-dividualsaredefinedasBMI25andindividualswithintermediateBMI25to30)areclassifiedasoverweight.Morbidobesityisdefinedas40andsuperobesityisdefinedasBMI50.Thesehighercategoriesofobesityareusedtobeextremelyrare,andtheystillarerelativelyrare.However,astheU.S.populationdistributionshiftstohighermeanBMI,theseextremeformsofobesityareincreasinginprevalenceatagreaterratethanthemean.AccordingtothemostrecentstatisticsfromtheU.S.CentersforDiseaseControl(CDC,2010data),allU.S.statesnowreportatleast20%obesityamongadults.Mississippi,WestVirginia,andAlabamacurrentlyreportthehighestrates(34.0%,32.5%,and32.2%,respectively),butseveralotherstatesarenotfarbehind.Worldwide,1.7billionpeopleareclassifiedasoverweight(Haslam&James,2009).Thesestatisticsposefun-novelproblemsforhealthmaintenanceanddeliverysystems.Thespeedwithwhichoverweightandobesityhavebecomeapublichealthcrisisisbreathtakingrause-fulmeta-analysis,seeFinucaneetal.(2011).ObesityintheUnitedStatesisas-sociatedwithadramaticincreaseintheprevalenceofobesity-associateddiseases,particularlycardiovasculardiseaseandType2diabetes,aswellashypertension,stroke,metabolicsyndromeandinsulinresistance,nonalcoholicfattyliverdis-ease,andsomeformsofcancer,notablybreastcancerinpostmenopausalwomenandadultcolorectalcancerinbothmenandwomen.About90%ofType2di-abetesisattributabletoexcessweight(Hossain,Kawar,&ElNahas,2007).TheincidenceofType2diabetes,inparticular,hasnowreachedepidemicpropor-tionsintheUnitedStatesandinternationally,affectingabout12%ofU.S.adultsandmorethan25%ofthoseovertheageof65.Type2diabetesisthoughttoberesponsiblefor4.6milliondeathsworldwideeachyear.Anoft-citedearlyesti-mateoftheincidenceofType2diabeteswas366millionworldwideby2030Wild,Roglic,Green,Sicree,&King,2004).However,morerecentestimateshavepeggedtheanticipatednumberofdiabeticindividualstobe439millionby2030(Shaw,Sicree,&Zimmet,2010),almostentirelyduetoobesity-drivenmetaboliccomplications.Thereisreasontoworrythatthispredictionwillsoonhavetoberevisedupwardyetagain.Unlessreversed,therapidlyworseningproblemofobesitypredictsancomorbiditiesthatwillstrainorbreakmanyhealthcaredelivery DisruptionCausesMetabolicallyHealthy systems,bothintheUnitedStatesandinternationally.Intheabsenceofna-tionalagreementabouttheproperroleofU.S.healthcaredeliverysystemswithcontrolledcosts,orpoliticalwilltodeliverwell-designedsolutions,theU.S.economyisuniquelyvulnerabletothisexpectedimpact.Thus,obesityposesacriticalchallengeofoverarchingimportanceforU.S.publichealth,particularlypediatrichealth:manyAmericanchildrenarealreadybeingsweptalongwiththisnationalwaveofprogressivemetabolicdysfunctioninobesity.Forthepurposeofthischapter,someofthegenesandepigeneticforcesthatdriveobesityandmetabolicdysfunctionwillbeexamined. 2.COMPLEXPOLYGENICINTERACTIONSWITHTHEENVIRONMENTANDEPIGENETICSINOBESITYWeliveinaneraofgeneticdeterminism.Majorefforthasbeeninvestedtoidentify“obesity-associatedgenes”withthetranslationalgoalofisolatingthe“drivers”fromthe“passengers,”muchthesamewaythatoncogeneshavebeenidentified,inordertodevelopnoveltherapeutictar-gets.Evidenceforageneticcomponentthatinfluencesriskforobesitycon-trollingforenvironmenthasbeendevelopedthroughstudiesofadoptionandtwins(Maes,Neale,&Eaves,1997,Silventoinen,Rokholm,Kaprio,).Geneticfactorsappeartoexplainasmuchas90%ofinBMIamongcertainmonozygotictwins.Furthermore,sev-eralrecentgenome-wideassociationstudieshaveestablishedconvergentvalidityinthediscoveryofgenesthatarestronglyassociatedwithobesitythroughoutthehumanlifespan.Thefirstrobustassociationwasreported(fatmassandobesityassociated)(Fraylingetal.,2007).Thisasso-joinedbyinsulin-inducedgene2(),melanocortin4receptor(),transmembraneprotein18(),glucosamine-6-phosphatedeaminase2(GNPDA2),neuronalgrowthregulator1(brain-derivedneurotrophicfactor(),andpotassiumchanneltetra-merizationdomaincontaining15(),asassociatedwithpediatricobesity(denHoedetal.,2010;Zhaoetal.,2009).Intensiveresearchinmo-continuesonotherwell-establishedlociofobesity-associatedgenes,includingthosethatencodetheuncouplingproteinsOppertetal.,1994;Ricquier,Casteilla,&Bouillaud,1991),peroxisomeLefebvreetal.,1998;Vidal-Puigetal.,1997),low-densitylipoproteinreceptor(Morris,Zee,&Robinson,1994hormone-sensitivelipase(Klannemarketal.,1998;al.,1997),betaadrenergicreceptors(Reynisdottir,Ellerfeldt, FangnianWangetal. Wahrenberg,Lithell,&Arner,1994;Walstonetal.,1995),andinflamma-torycytokinegenessuchastumornecrosisfactor(TNF)-Henry,&Kern,1996)andinterleukin-6(Kern,1997;Kern,Ranganathan,Li,Wood,&Ranganathan,2001).Thehopeofthesestudieshasbeenthat,throughidentificationandcharacterizationofcandi-dategenesforobesityandmetabolicsyndrome,potentnewdrugswillbedevelopedthatspecificallytargettheseproteinsorpathwaysandwillhavetherapeuticvalueforprediabeticordiabeticobesepatients.Althoughmorethan100geneshavebeenidentifiedthatinfluencebodyweight(Leibel,2008),theusualpatternsandrulesofMendelianinheritanceinadequatetounderstandtheinheritanceofpredispositiontometabolicsyndromeandType2diabetes.Atleast18geneshavebeendirectlyassociatedwithType2diabetes(Florez,2008;Ridderstra).Thisfactindicatesthat,unlikeinbornerrorsofmetabolism,suchasTay–Sachsdisease,forwhichastraightforwardcausalconnectionex-istsbetweenamutantalleleandawell-characterizeddysfunction(),thegeneticmechanismsthatpromoteincreasedrisksinobesityforType2diabetes,cardiometabolicdiseases,andobesity-associatedcancersarenotsostraightforward.Itisalsoclearthattheinteractionofgenesaloneisinsufficienttoexplainthecontemporaryproblemofobesity.Inviewofthenewinternationalen-vironmentofwidespreadovernutrition,italsoseemsimportanttoaskhowgenesrespondtoweightgainorweightloss,notjusthowspecificgenesmakeusfatorthin.Dietarycaloricexcessthatistotallymisalignedwithphysicalenergyexpenditurecharacterizesthisenvironment.Epidemiolo-gistsandU.S.publichealthofficialshavetakennoteofcriticalfeaturesofthecurrentAmericanenvironment,particularlyeasyaccesstocheapcalo-ries,theprofligateuseofsugarsweetenerslike“highfructosecornsyrup”inthefoodindustry(Duffey&Popkin,2008;Popkin,2007;Popkin&andwidespreadoverconsumptionoffried,fatty,“fast”foods.Tenthousandyearsofhumanevolutionhavetendedtoproducealeanphysicalphenotype.Indeed,severepediatricobesityofgeneticoriginisob-servedinlessthan0.01%ofthepopulation(Farooqi&O’Rahilly,2006,thedramaticallyincreasedprevalenceofoverweight,obese,andmor-bidlyobesephenotypesinthepastdecadesofthetwentiethcenturyandfirstdecadeofthetwenty-firstcenturymustbeattributableprimarilytoenviron-mentalandconsumptionchanges,i.e.,environmentalobesogenicpollutants,reducedenergyexpenditureanddiet-inducedobesity.Strongevidencefortheroleoftheenvironmentwhengeneticfactorsarerelativelywellcontrolled DisruptionCausesMetabolicallyHealthy wasobtainedfromstudiesofthePimaIndians,anaboriginalpopulationthatlivesinthedesertsouthwestoftheUnitedStatesandinanareaofnorthernMexicowithasimilarclimate.Thegeneticvariationbetweenthetwopopulationsisrelativelysmall.PimaIndiansintheUnitedStatesareonaverage25kgheavierthanPimaIndiansinMexico(Ravussin,1995),withespondingdifferencesincardiometabolicrisk.Thesedifferenceshavebeenattributedprimarilytodiet.Alternatively,populationpatternsofobesitymaybeattributedinparttoepigeneticshifts,nottomutationinhumanDNA,becausethetimescaleonwhichthesechangesinpublichealthhaveoccurredarefartoorapidtobedueprimarilytoevolution.Thereisnewinterestinthematernal–fetalenvironmentandanefforttounderstandapotentialroleforepigeneticmechanismsinthetransmissionofmetabolicriskfactors.TheepigeneticmodificationsofnucleosomalhistonesandDNAthatunderliethesephenomenaarepoorlyunderstood.Thesemod-ificationsincludeDNAmethylationandhistoneacetylationorphosphoryla-tionandarecriticalforpropercontroloftheresponseofpromoterstosignaltransductioninthedifferentiatedcellsoftheadult(Bernstein,Meissner,&er,2007;Li,Carey,&Workman,2007),aswellasforembryonicandfetaldevelopment(Bernsteinetal.,2006).Indeed,someofthemostinterest-workonepigeneticanddevelopmentalmechanismshasbeenconductedinratdamsfedahigh-fatdiet.Investigatorshaveidentifiedalterationsinho-meoboxgeneexpressionpatterns,suchasHoxA10,thatlikelyinfluencestemcellfatechoiceinosteogenicandadipogeniccelllineages(Chenetal.,2012sealterationsoftranscriptionalprogrammingdependcriticallyonpatternsofacetylationandmethylationofhistonelysinesinnucleosomalchromatinatkeytargetgenes.Thisconceptsuggeststhatpatternsofobesityandmetabolicdysfunctionmayindeedruninfamilies,butnotinthesamewayorsubjecttothesamemechanismsaspatternsoffamilialcancers.Onefamousandwell-studiedcasethatstronglysupportsanepigeneticmechanismforcardiometabolicriskistheDutch“HungerWinter”of1944–1945.Thiswartimeevent,whenseverestarvationaffectedthewesternNetherlands,revealedindetailforthefirsttimethatepigeneticmechanismsplayacriticalroleinhumanBMIandinsulinsensitivity.Spe-cifically,maternalhungercreatedbycold,harshlivingconditions,andca-loricdeprivationofpregnantmotherswaslinkedtoinsulinresistance,obesity,anatherogeniclipidprofile,andelevatedcardiovascularriskinthesurvivingchildrenastheyaged(Kyle&Pichard,2006).Ofparticularborntothesamemothersintimesoflessseveredeprivationdidnotshowthesameriskpatterns.Morerecentworkhasshownthat FangnianWangetal. infantsborntoobese,overweight,andType2diabeticmothersdisplayin-creasedadiposityandelevatedriskforlatermetabolicdisease(&Friedman,2010).Inaddition,aUKstudyfoundthatmaleswhoweremostunderweightatbirthwereseventimesmorelikelytodevelopmetabolicdysfunctionandType2diabeteslaterinlifethanmaleswhowereheaviestatbirth(Halesetal.,1991).Thereisstrongsupportforanbetweenbirthweightandhypertensionintheadult,forbothmenandwomen,inwhichlowbirthweightpredictsriskamongthehighestweightadults(Barker,Osmond,Golding,Kuh,&Wadsworth,).Theseobservationssuggestthatmaternaluterineenvironmentsvarythatcreatestableandlastingconsequencesforthemetabolicpatternsofoffspringexposedtothatenvironmentduringgestation(Barker,1995thesepatternshavebeenascribedtoepigeneticmodificationofkeygenesthatregulateenergymetabolism.Suchmechanismshavebeenandcontinuetobeexploredandvalidatedinrodentmodels(Levin&Nathanielsz,Poston,&Taylor,2007;Samuelssonetal.,2008;Shankaretal.,2008).Thus,newresearchfocusingonthespecificnucleosomalhistonesinchromatinandDNAisworthyofattention.InterestingworkhasshownthatmanipulationofDNAmethylationpathwaysbymetabolicsupplementationcanaltertheintergenerational,epi-geneticpatternsofobesity(Waterland,Travisano,Tahiliani,Rached,&whichdirectlyaddressesmechanismsthatmayberelevanttotheHungerWinteroffspring.Suchapproaches,ifvalidatedwithanimalmodelsandinclinicaltrials,offerthepossibilityofa“personalizedmedicine”approachtoobesitytherapeutics(Cordero,Campio&Milagro,).InnovativeclinicalinvestigationstomeasurehowanalteredmaternaluterineenvironmentduringgestationaffectsDNAmethylationpatternshavealreadybeenreported(Cooperetal.,2012modificationsarewellstudiedinembryogenesisandcancer(Sharma,Kelly,&Jones,2010),muchlessisknownabouttheirmetabolicdiseases.IntenseresearchisnowfocusedonhowDNAsequence-specifictranscriptionfactorssuchasPPARandtranscriptioncoregulatorssuchasPGC-1Puigserveretal.,1998)interactwithhistonesremodelers(Pedersen,Kowenz-Leutz,Leutz,&Nerlov,)toalterchromatinandreprogramgeneexpressionnetworksJaenisch&Bird,2003).Thesetranscriptionalcoregulatorfunctionsarealsoinflammation(Freund,Orjalo,Desprez,&Campisi,2010;Orjalo,Bhaumik,Gengler,Scott,&Campisi,2009),whichplaysacritical DisruptionCausesMetabolicallyHealthy roleinthedevelopmentofinsulinresistanceinobesity(Bastardetal.,2006;Shoelson,Herrero,&Naaz,2007stoneacetylationisalsobeingconsideredasarelevanttargetforepige-neticmanipulationtoaffectenergymetabolism.Forexample,genome-widepatternsofhistoneH3acetylationatlysine9and18havebeenreportedinINS-1cells,aratmodelforthepancreatic-cell,uponexposuretopeptideincretinhormones(Kim,Nian,&McIntosh,2009).Thesemodificationsalternscriptionalcoregulatorfunctionwhichlikelycoordinatesreprogrammingoftranscriptionalnetworksthatrespondtoglucosesignaltransductioninthe-cell.Thisapproachmayhavetranslationalsignificanceforobese,insulin-resistantpatients,becausethesepeptidehormonespotentiateglucose-stimulatedinsulinsecretionintheislet,amongothereffects.Ontheotherhand,increasedhistoneacetylationhasbeenwidelyappreciatedfordecadesasamarkoftranscriptionalactivationatnumerousloci.Absentamorespe-cific,promoter-defined,or-cell-specificsignatureofhistoneacetylationthatisuniqueandresolvablefromthegeneralsomaticpattern,theseinsightshaverelativelymodestutilityandpresentnonewtherapeutictargetsforType2diabetes.Theemergingpracticalityofmanipulationofchromatin-controlledtranscriptionalprogramsfortherapeuticbenefitispotentiallyusefulinviewofthenewavailabilityofaclassofbromodomainprotein-directed,small-moleculeinhibitors(Belkina&Denis,2012;Filippakopoulosetal.,2010;leretal.,2011Nicodemeetal.,2010).Ifspecific,functionaltargetsofhistoneacetylationcouldbeidentified,small-moleculetherapeuticsforaber-ranthistoneacetylation/transcriptionalcoactivationmaydevelopanexperi-mentalbasisforanimalmodelexperiments.However,thefieldhasnotyetreachedthisstageofdevelopment.ActivatorsofPPARfunction,suchaspioglitazone,alsoappeartoplayaroleintranscriptionalprogrammingcontrolledbyPPARinpartthroughal-terationofhistonemodifications.Inthe-cell,increasedmethylationofhis-toneH3atlysine4inthepromoterregionsofIns1Ins2,andGlut2genesismaintainedthroughthedimethyl-lysineregulatingcomplexSet7/9methyl-transferaseandisrequiredforpropertranscriptionoftheseloci(Deering,hara,Trace,Maier,&Mirmira,2009).Pioglitazonetreatmentofobese(leptinreceptor-deficient)miceorhigh-fatdiet-fedwild-typemice,whichiswellknowntoimprovemetabolism,dramaticallyimprovesinvivotranscriptionofIns1Ins2,andGlut2genes.Thisimprovementisassociatedwithincreasedhistoneacetylationofthesekeytargetgenes(Evans-Molinal.,2009).SimilarenrichmentinmethylationofhistoneH3atlysine4hasbeenreportedin-celllinesandislets,andparallelincreasestranscriptionofthesesamegenes(Francis,Chakrabarti,Garmey,&Mirmira,2005 FangnianWangetal. Innormalhumanpancreaticislets,histonelysinemethylationpatternshavebeenidentifiedthatdefinetranscriptionally“primed”aswellastranscription-allyactivepromoters(Bhandareetal.,2010),butthisveinofresearchisrel-velyunderdeveloped,comparedtothestudyofhistonelysinemethylationincancer.Additionalexperimentstotestmechanistichypothesesarecriticallyneededtodeepenunderstandingofhowmanipulationofchromatin“readers”and“writers,”andDNAmethylationenzymes,mightbemobilizedtherapeu-tically(Belkina&Denis,2012)toimproveldysfunction.Mostoftherelevantworktodatehasbeennomorethancorrelative. 3.THEbrd2loMOUSEMODELOFMETABOLICALLYHowaretheseenginesofhistonemodification(the“writers”oftheepigenome)andthetranscriptionalmachinesthatrespondtosignaltransductiontointerpretthesemodifications(the“readers”oftheepigenome)tobestudiedandunderstoodintheirregulationofdiversetran-scriptionalnetworks?Animalmodelsthatenablemanipulationofchromatinandepigeneticmechanismswillobviouslybecomeincreasinglyimportantasinvestigatorsseektounderstandtherelevantgenesandsignaltransductionpathwaysatworkinobesity.Inparticular,onemodelwithanepigeneticbasisforobesityhasreceivedattentionrecentlyandoffersanovelinterpretivetool:theBrd2-deficientmodelfor“metabolicallyhealthy”obesity.Inbothhumansandmice,thegeneencodesanunusualtranscriptionalcore-gulatorthatcontainsdoublebromodomains(Haynesetal.,1992;Horn&rson,2001;Jeanmougin,Wurtz,LeDouarin,Chambon,&Losson,1997;Winston&Allis,1999).Brd2belongstothebromodomainanddomain(BET)familyoftranscriptionalcoregulatorsdefinedbytwotandem,mutuallyrelatedbromodomainsattheamino-terminusofthepro-teinthatbindtoacetylatedlysinesinnucleosomalchromatin(Kannoetal.,2004;muraetal.,2007),particularlyacetylhistoneH4(Umeharaetal.,2010)andtranscriptionallycouplehistoneacetylationtogeneactivation(Rickards,&Flint,2008).Theamino-terminaldualbromodomainsinthisfamilyarefollowedbyan“extraterminal”domainthatisinvolvedinprotein–proteininteractions(Linetal.,2008;Rahmanetal.,2011),thusthe“BET”familyname.romodomainistheonlyproteinstructuralmotif(Dhalluinetal.,1999)thatiscapableof“reading”sitesofhistoneacetylationinnucleosomalchromatinSanchez&Zhou,2009).Brd2studieshavebeenimportantbecausetheyhavealedremarkableandunexpectedrolesforchromatinregulationinenergy DisruptionCausesMetabolicallyHealthy 3.1.GenetargetingofthelocusinmiceTargeteddisruptionoftheBrd2gene,whichislocatedintheclassIImajorhistocompatibilitycomplex(MHC)nearTnf,causesextremeobesitywithhyperinsulinemia,butalsohypoglycemia,hyperadiponectinemia,andim-provedglucosetolerancequitedistinctfromotheranimalmodelsofobesity(Wangetal.,2009d2dnopreviouslyknownlinktoobesity,insulinsensitivity,orenergymetabolism(Belkina&Denis,2010;Denis,kolajczyk,&Schnitzler,2010).Thegenewasdisruptedinmouseembry-onicstemcellsbyinsertionofalacZcassettethatencodes-galactosidase.ThecellswereengineeredbyBayGenomicsattheUniversityofCalifornia,Davis,whichisanarmoftheMutantMouseRegionalResourceCenters,andwhichreceivessupportfromtheNationalInstitutesofHealth(http://www.mmrrc.catalog/overview_BG.php).Twotypesofembryonicstemcellswerede-veloped,onewithalacZinsertioninthecodingregionofthegene(designatedRRE050)andonewithalacZinsertioninthepromoterregion(designatedRRT234).Theselattercellswereusedtodevelopthebrd2lomice(Wangetal.,2009).Thephenotypecouldnothavebeenpredicted(Wangetal.,2009),yetholdsoutthepossibilityofamoreunified,epigenetically-basedmechanismthatunderliesseveralhumancomorbiditiesassociatedwithobesityandinflammation(Denis,20103.2.Systemic,protectivephenotypesinbrd2loDespitesevereobesityapproaching100g,brd2loanimalsshowimprovedwhole-bodyinsulinsensitivityanddonotdevelopinsulinresistanceorglu-coseintolerance.Theyshowbetterwhole-bodyinsulinsensitivitythanwildtype,controlanimalsontheC57Bl6/Jbackground,despitedramaticobesity(Jornayvazetal.,unpublisheddata).Severalwhole-bodymechanismslikelycontributetothisprotection(Wangetal.,2009).Forexample,althoughbothmalesandfemales,consumeslightlymorechowthanage-andsex-matchedwild-typecontrols,theyburnslightlymorecaloriesasheatinisothermalhousing.Theanimalscarrymoreinterscapularbrownad-iposetissueandtheirwhiteadiposetissueexpresseshigherlevelsofuncouplingproteins,whichprovidesamitochondrialmechanismforin-creasedheatproduction.Thisphenotypeisknowntobeprotectiveofme-tabolisminobesity.Inaddition,brd2lomiceshowarespiratoryexchangeratioofoxygenconsumptionandcarbondioxideproductionthatissugges-tiveoffatmetabolismatalltimesofdayandnight,fedstateorfastingstate,ratherthanashiftbetweencarbohydratemetabolismexpectedforthefed FangnianWangetal. statetofatmetabolismexpectedforthefastedstate(Wangetal.,2009).Con--oxidationoffattyacidastheprimaryenergysourcemightbeexpectedtobemetabolicallyprotective,althoughthemitochondrialbasisforthispreferredmechanismofenergymetabolismisnotunderstoodinthesemice.Finally,productionofhigh-molecularweightadiponectin,aninsulin-sensitizingadipokine,waselevatedalmosttotheserumlevelsseeninadiponectintransgenicmiceonthe(leptindeficient)backgroundKimetal.,2007).Elevatedadiponectinconfersyetanotherlayerofmeta-inobesity.Yetitisimportanttopointoutherethattheadiponectinpromoterhasnotbeendirectlygeneticallymanipulatedinthesourceembryonicstemcells;thisresultsuggeststhatBrd2coregulatorfunctionisordinarilyrequiredforcorepressionofadiponectintranscription.Thishypothesishasnotyetbeentestedexperimentally.3.3.Thebrd2lophenotypeprotectsadiposetissueRemarkably,knocked-downexpressionofBrd2inthe3T3-L1different-iationmodelalsoprotectsculturedadipocytesfromTNF--inducedinsulinresistanceinvitro,probablybyuncouplingTNFreceptorsignalingfromtran-scription(Wangetal.,2009).TheeffectofreducedBrd2levelsalsoocopiestheactionofthiazolidinedione(TZD)drugs,suchasrosiglitazoneandpioglitazone,whichareusedasinsulinsensitizers.Brd2coactivatorfunc-tionopposestheactionofPPAR;Brd2proteinassociateswithPPARpro-teincomplexesandknockdownofBrd2stronglystimulatesPPARdependenttranscriptionandadipogenesisin3T3-L1cells(Wangetal.,20093.4.InsulinresistantobesityisaninflammatorydiseaseInsulinresistanceinthecontextofobesityisassociatedwithachronicstateofsubclinicalinflammation(Bastardetal.,2006;Shoelson,Lee,&Goldfine,2006;Weisbergetal.,2003;Xuetal.,2003),includingincreasedserumcon-rationsofC-reactiveprotein,interleukin-6,interleukin-8,andTNF-patientsanddifferentanimalmodelsofobesity(Kahnetal.,2006).Ininsulin-istantobesity,productionofTNF-inliver,fat,andmusclebyinfiltrating,proinflammatory(M1)adiposetissuemacrophagespromotesinsulinresistancedirectly(Hotamisligil,Shargill,&Spiegelman,1993).Here,M1macrophagesdistinguishedfromthemoreremodeling-purposed,alternativelypolarized“M2”typeofmacrophage.Commonly,proinflammatorymacrophagesinfil-tratewhiteadiposetissueinpatientsanddifferentanimalmodelsofobesityKahnetal.,2006),formingcharacteristic,histologicallyidentifiablepatterns DisruptionCausesMetabolicallyHealthy ofleukocytescalled“crown-likestructures”(Apovianetal.,2008;Cancelloetal.,2005,Cintietal.,2005)thatsurroundstressed,dead,anddyingadipo-s,andarecloselyassociatedwithmetabolicrisk.Thesestructureshavere-centlybeenshownalsotocontainBcells(McDonnelletal.,2012),andbothTsandBcellsengageincrosstalkwithperipheralbloodmonocytestodefinetheproinflammatoryandanti-inflammatorybalanceofcytokinesintheobese,insulin-resistantadult(Jagannathanetal.,2009,2010).Toafirstapproxima-n,thegreatertheproinflammatorybalance,thegreaterthemetabolicdys-functionandthemoreadvancedthedisease.However,muchworkremainstobedonetounderstandthespecificTcell,Bcell,andmacrophagesubtypesthatarerequiredfordiseaseprogression,theanti-inflammatoryandhomeostaticmechanismsthatopposeaggravatedchronicinflammation,andthekineticsofentryontoanddeparturefromthemetabolic“theatresofaction”ofeachofthesecelltypes:thecentralandperipheraladiposedepots,theliver,thepan-creas,andtheblood.3.5.Metabolicallyprotectivephenotypesinthebrd2loimmunesystembrd2lomiceexhibitbroad-spectrumprotectionagainsttheinflamma-torycomplicationsofobesity(Wangetal.,2009).Inflammatoryresponsesaremildlydeficientintheseanimals(Belkina,Blanton,Wang,Liu,&whichlikelycontributestotheirprotectionagainstmeta-bolicdysfunction.Theseobservationsleadtonovelhypothesesaboutthein-teractionsandcrosstalkbetweenadipocytes,macrophages,andTcellsthatcontroltheinflammatorystateofadiposetissue.Whiteadiposetissueshowsreducedinflammation:bonemarrow-derivedmacrophagesunderproduceproinflammatorycytokines(Belkinaetal.,2010,2013),Tcellmigrationisted(G.V.Denisetal.,unpublishedobservations),andregulatoryTcellsareexpanded(G.V.Denisetal.,unpublishedobservations).Furthermore,be-causepolarizationofmacrophagestotheanti-inflammatory,proremodeling(M2)staterequiresPPAROdegaardetal.,2007),increasedPPARvitybrd2lomacrophagesandelevatedserumadiponectin(Ohashietal.,2009)islikelytopromoteM2polarization,alsoprotectingagainstinflammation-driveninsulinresistance.Bytranscriptionallyuncouplingobesityfrominsulinresistance,themildhypo-inflammatoryphenotypeofthebrd2lomodelfo-cusesattentiononTcellandadiposetissuemacrophagemechanismsthatlikelyprotect“metabolicallyhealthy”obeseindividualsandmightbeharnessedtoprotectthelargerpopulationofobesepatientswithinsulinresis-tance.Consistentwiththeinflammatorymechanism,areportinNature FangnianWangetal. Geneticshasidentifiedhumansinglenucleotidepolymorphisms(SNPs)intheBRD2locusthataresignificantlyassociatedwithrheumatoidarthritis,whichisdrivenbyautoimmuneandinflammatoryprocesses(Mahdietal.,2009hermore,BRD2variantsmaybeassociatedwithBMIinPimaIndiansMuller,Abdussamad,etal.,2011).Upregulationofproinflammatorykinegeneshaslongbeenappreciatedtopromoteinsulinresistanceandglucoseintolerance,whichprecedeseriousmetabolicdysregulationthatleadstoType2diabetes(Pickup&Crook,1998inflammationprotectsagainstinsulinresistanceandcharacterizeshuman“metabolicallyhealthy”obesepopulations.Thesehumansubjectsdisplayattenuationofeachof:glucoseintolerance,dys-lipidemia,hyperuricemia,andhypertension(Bonoraetal.,1991;al.,2008).Therefore,controlofadiposetissue-infiltratingin-flammatorycellsandtheirchromatin-regulatedgeneexpressionholdspromiseforinsulin-resistancepatients.Inobesity,macrophages,Tcells,andadipocytesproduceproinflammatoryandanti-inflammatorycytokines,chemokines,andadipokines.Giventhatthesefactorssynergizewith,antagonize,andregulateeachother,therearemanyunansweredquestionsaboutwhathappensduringtheadipocyte–macrophage–TcellinteractionsKintscheretal.,2008),andhowandwheninsulinresistancedevelops.proposedthattheseanimalsofferanovelmodelforhuman“met-abolicallyhealthy”obesity.Themodelmotivatesinterestingandinforma-tivehypothesestotestthelinksamongleukocytemigration,proinflammatorycytokineproduction,andinsulinresistanceinobesity. 4.WHOAREMETABOLICALLYHEALTHYInmosthumans,themaineffectofincreasingBMIisanonlineardete-riorationinmetabolicandcardiovascularhealth.Thisprocesshasbeende-scribedasagradualclusteringoftraitsthatincludevisceralobesity(asdistinctfromelevatedBMI),insulinresistance,dyslipidemia,hypercholesterolemia,andhypertension.Intheclinic,insulinresistancestatusisoftendeterminedbythehomeostaticmetabolicassessment(HOMA),whichisassessedusingtheformula:fastinginsulin(U/mL)fastingglucose(mg/dL)/405Ditschuneit,Flechtner-Mors,Johnson,&Adler,1999;Matthewsetal.,Asastringentmeasureofinsulinresistance,avalueofHOMA2isoftenapplied.AccordingtotheoriginalAdultsTreatmentPanelIIIof2001,amet-icsyndromediagnosisisrenderedwhenthreeormoreofthesefivecriteria DisruptionCausesMetabolicallyHealthy arefulfilled:fastingplasmaglucoseconcentrationofatleast110mg/dL,waistcircumference88cmforwomenand102cmformen,serumhigh-densitylipoproteinconcentration50mg/dLforwomenand40formen,bloodpressureof130/85mmHg,andserumtriglycerideconcentrationof150mg/dL(Grundyetal.,2005).TheInternationalDiabetesFederation/ricanHeartAssociation/NationalHeartLungandBloodInstituteunifiedcriteriaaresimilarandrequirethreeoftheabovecriteria,includingtheabovecutpointsfortriglyceridesandbloodpressure,andacutpointforfastingglucosemorestringentthanATPIII(100mg/dL)(Albertietal.,2009)withaddedcriteriaofcentralobesity,drugtreatmentfordiabetes,elevatedtriglycerides,lowlevelsofhigh-densitylipoprotein,orhypertension.Never-theless,thereisnouniversallyaccepteddefinitionofmetabolicsyndrome.Therehasbeendisagreementintheliteratureabouttheoptimalcriteriatouseformetabolicdysfunctioninobesitybecauseriskincertainhumanpopulations,suchasspecificethnicgroups,forcertaindiseasessuchascardiovasculardisease,maybebetterpredictedbysomecriteria,suchasglucoseintolerance,thanbyothers,suchasmetabolicsyndrome.Oralglucosetolerancetestsandcriteriaforimpairedfastingglucoseandimpairedglucosetolerancehavebeenusedtosupplementthediagnosisofmetabolicsyndrome,butdiscussionofthisliteratureisbeyondthescopeofthischapter.However,itispertinentthat,asmentionedabove,certainobeseindivid-ualsare“metabolicallyhealthy”andenjoyreducedriskforcardiovasculardiseaseandType2diabetes(etal.,2010;Sims,2001;Succurroal.,2008;Wildmanetal.,2008).“Metabolicallyhealthy”obeseadultsdefinedasabdominallyobese(BMI30)butlackingmetabolicsyndrome(Meigsetal.,2006).Suchindividualscompriseabout25%ofthepopulationintheUnitedStates,however,thisprevalencede-pendsoninclusioncriteria,withsomereporteddisagreementinprevalence,fromaminimumof11%ofobesesubjectsinanItalianstudy(Calorietal.,)to47.9%ofobesesubjectsinaKoreanstudy(Lee,2009).The“met-obesephenotypeisbestconceptualizedasacontinuousdistributionofpreservedinsulinsensitivityasafunctionofincreasingBMISomeoftheseindividualsshowprotective,elevatedlevelsofadiponectin(etal.,2008)andmaintainnormalglucosetol-erancedespitestartlinglyhighBMI.Factorsthatcoupleobesitytoinsulinresistanceandmetabolicsyndromeareofgreatmedicalinterest,becausetheyunderlietheetiologyofobesity-drivenType2diabetes.Thus,the“metabolicallyhealthy”obeseindividualislikelytoprovideagoldmineofinformation.Thestudyofthispopulation FangnianWangetal. forgenesandpathwaysthatcoupleobesitytoinsulinresistancehasthepo-tentialtoidentifynovel,“druggable”targetstohelpunhealthyobesepatientsavoidtheworstcomorbiditiesoftheircondition.Significantly,the“meta-bolicallyhealthy”obesephenotypeisassociatedwithareducedinflamma-toryprofile(Karelisetal.,2005;Romanoetal.,2003).Thus,itislikelythatoftheinnateandadaptiveimmunesystemareessen-tialtolinkobesitytoinsulinresistance,cardiometabolicrisk,andType2di-abetes.Greaterdetailconcerningtheimmunecellsubtypes,theircytokineproductionprofiles,andkineticsofmobilizationintheinsulin-resistantobesesubject,andhowthesedifferincriticalwaysformthe“metabolicallyhealthy”obesesubjectisurgentlyrequired. 5.OTHERANIMALMODELSOFAdditionalmechanisticunderstandingofhowthispopulationofhumansisprotectedfromobesity-drivencomorbiditywillbeachievedthroughhypothesisbuildingandtestinginanimalmodels.Beyondtheex-ampleofbrd2lomice,thereareother,fundamentallydifferenttypesofan-imalmodelsavailable,somethatareprimarilyimmunological,whileothersareadiposetissuedirected.Thesedifferentmolecularandcellularperturba-tionsordeficiencieswillenablemoreprecisemechanisticexplorationoftherelevantpathwaysthatcoupleobesitytoinsulinresistance.Low-inflammatorymodelsinclude1knockout:Areducedinflammatoryprofile,particularlylowerlevelsofTNFandinterleukin-6,appearstoprotecttheseanimalsfromhigh-fatdiet-inducedinsulinresistanceandglu-coseintolerance(McGillicuddyetal.,2011Induciblenitricoxidesynthaseknockoutpolarizationofmac-rophagesasaresultofknockoutofprotectsagainstobesity-inducedskeletalmuscleinsulinresistance,andthisisassociatedwithimprovedphosphoinositide3-kinase/Aktactivity(Perreault&Marette,2001AblationofTNFagainstTNFimprovesinsulinresistanceinobesity(Hotamisligiletal.,1993),andmicedeficientinTNFsig-nalingareprotectedfrominsulinresistanceinobesity(Wiesbrock,Marino,&Hotamisligil,1997TWEAKknockoutweakinducerofapoptosis(TWEAK),acytokineoftheTNFsuperfamily,isimportantnotonly DisruptionCausesMetabolicallyHealthy fortissueremodelingafterinjury(Burkly,Michaelson,Hahm,Jakubowski,&Zheng,2007)butalsoforremodelingofadiposetis-suetoaccommodateincreasedstorageinobesity(Lietal.,2009TheTWEAKpathwayisactivatedinobeseType2diabeticpatientsnetal.,2006).TWEAKdeficiency(Campbelletal.,2006shiftsmacrophagepolarizationtothealternatively-activated“low-inflammatory”phenotype,increasescollagenturnover,andde-creasesJNKactivationingonadaladiposetissue,conferringmeta-bolicprotectioninobesity(M.S.Obin,TuftsUniversity,SchoolofMedicine,personalcommunication).:ExpressionintheliveroftherepressorofNF-signalingprotectsagainsthigh-fatdiet-inducedandlowlevelNF-B-inducedinsulinresistance(Caietal.,2005AdiposetissuemodelsincludeCollagen6knockoutcapabilityofadiposedepotstoremodelandacceptincreasedstorageinobesityappearstoreduceadipocytestressandapoptosis(Khanetal.,2009).Thisincreasedcapacitydependsonlossofcollagen6,andimprovesfastingglucoseandglu-cosetoleranceperhapsbyrelaxingphysical,stericconstraintsonad-iposedepots.Adiponectintransgenicobesitywithinsulinresistanceonan(leptindeficient)backgroundcanbeamelioratedinadramaticfashionbytransgenicexpressionofadiponectin(Kimetal.,2007),afactorthatsensitizescellstoinsulinsignaling.Suchmousemodelswillbeusefultorevealdifferentkindsofmetabolicpro-howcrosstalkmayalsoprotectorgansystemsfromcomorbiditiesDenis,2010 6.DEREPRESSIONOFINSULINTRANSCRIPTIONINTHEbrd2loAdeeperunderstandingofthemechanismsthatcontrolmaternal–fetaltransmissionofincreasedriskforType2diabetesiscriticalatthisstageoftheobesityepidemic.Thereissignificantevidence,obtainedinitiallyfromstudiesofthePimaIndians,thatmotherswithType2diabetescanconferelevateddiabetesrisktooffspring(Dabelea,2007;Dabelea&Pettitt,etal.,2000,2008).ThedevelopmentofType2diabetesisdependentonboththegraduallydecreasingmetabolichealthoftheobeseindividualasinsulinresistanceandinflammationincreases,aswellasstrain FangnianWangetal. -cellproductionofinsulinthateventuallyleadsto-cellfailure.Thequestionofhowepigeneticmechanismsinfluencethedistinctbutrelatedriskstodeclininginsulinactionandinsulinproductionhasnotbeenwell-cellproliferationanddifferentiation,aswellasincreasedin-sulintranscriptionandreleasefrompancreaticinvivo,undoubtedlyprotectsobesebrd2loanimalsfromprogressiontoglucoseintoleranceand-cellfailure.Isletsshownosignsofapoptosisorstressbutareexpandedfromanearlyage,likelyasanearlyperturbationtoislethomeostasisthatisdirectlyattributabletoBrd2reduction,nottoinsulinresistanceinthepe-riphery(Wangetal.,2009thepotentialsignificanceofreducedBrd2expressiondur-ingdevelopment.WewantedtoknowifreducedBrd2expressionintheem-bryonicstemcellsofRRE050orRRT234origin(Wangetal.,2009)hadteredbiologyrelevanttoenergymetabolism.Basedonpublishedresultsofinsulin1genetranscriptionin-celllines,wehypothesizedthatinsulintranscriptionwouldbepotentiatedintheRRE050orRRT234cells.Accordingly,wetransfectedRRE050embryonicstemcellswithaneGFPreporterconstructfortheIns1promoter,obtainedasagenerousgiftfromDr.ManamiHara,thenselectedthecellsunderhygromycinasshowninFig.3.1markably,thisresultshowsthatreducedlevelsofBrd2proteinpoten-tiatetranscriptionoftheinsulingeneextremelyearlyinmousedevelopment,evenbeforetheembryonicstemcellhaslosttotipotentcharacteristicsduringthecourseofinvitrodifferentiation.OnepotentialimplicationofthesedataisthattargetedinhibitionofBrd2orgeneticmodificationofembryonicstemcellscouldprovideatherapeuticstrategyfor-cellfailurethroughregen-erationof-cellmass,orforgenetherapyforType1diabetes.Epigeneticallybasedtherapeuticsformetabolicdysfunctionarethereforefeasible,althoughdetailedmechanisticstudiesareobviouslynowrequired. 7.TRANSLATIONALIMPLICATIONSOFEPIGENETICREPROGRAMMING:CONCLUSIONSApartfromthematernal–fetaltransmissionofincreasedcardio-metabolicriskintheHungerWintercase,otherprocesseswithapotentialepigeneticcomponentarelikelyatworkinobesity.Forexample,weightregainafterbariatricsurgeryhasemergedasaworrisomeproblemforclini-cians(Magroetal.,2008).Overthelongterm,asignificantfractionofbar-(20.4%formorbidlyobesepatientsand34.9%forsuperobese DisruptionCausesMetabolicallyHealthy patientsinonestudy)(Christou,Look,&MacLean,2006)regainsignificantweight.Forthefractionofpatientsforwhomregainisunrelatedtosurgicalfailure,itispossiblethatepigeneticfactorsplayaroleinthedifficultywithmaintaininghealthyweightinthe10-year-periodthatfollowssurgery.Likewise,dietandlifestylemodificationfortheless-morbidlyobesealsoshowsonlymixedsuccess.Important,outstandingquestionsremain.Itisunclearwhetherthereisanepigeneticcomponenttothe“metabolicallyhealthy”obesepheno-type,eitherinhumansorinmice.Studiestomeasureamaternalgenetic bGH-PAvisvisInsE14 parentalHgrDifferentiatedUndifferentiatedEmbryoid bodies Figure3.1ReducedexpressionofBrd2potentiatesinsulintranscriptioninembryonicstemcells.(A)Schematicofmouseinsulin1promoterthatdrivesexpressionofeGFP).Promoterelementsarealsoshown:bovinegrowthhormonepolyAsequence)andhygromycinresistance().(B)Visual()andfluorescence()mi-crographsofEScellstransfectedwiththeconstructin(A)andpermittedtoundergodifferentiation.Undifferentiatedcellswereculturedongelatin-coatedtissuecultureplasticinthepresenceofleukemiainhibitoryfactor(LIF)(undifferentiated),thenLIFwaswithdrawntopermittheformationofembryoidbodiesfor2weeks(embryoidbod-ies),andculturewascontinuedforanadditional2weekstopermitadditionaldifferen-tiation(differentiated).Magnificationisshownattheright-handedgeofthefigure.TheparentalEScells(E14parental)werecomparedtoBrd2KOEScells()asdescribedinWangetal.(2009),atthesamestageofdifferentiation. FangnianWangetal. contributiontoBrd2-regulatedmetabolismhaveyettobeperformedinmice.ThereissomeevidenceformaternallydefinedDNAmethylationpatternsinbrd2lomice(F.Wang,unpublishedobservations),butadditionalexperimentsarerequiredtoaddressthisissue.Becauseishomologoustoaknown“maternaleffect”genein,calledfemalesterileBeck,Hanson,Kelly,Pappin,&Trowsdale,1992;Denis&Green,etal.,1986),wehaveproposedthatBrd2-regulatedmetabolismamaternaleffectinhumansandmice(Belkina&Denis,2012;Denis,2010Finally,wespeculatethatepigeneticmodificationsthatatten-uateexpressionofthelocusinhumans,nearby,orothergenesthatencodeproinflammatoryfactors,willbepresentin“metabolicallyhealthy”obesepatients,butmodificationsthatexacerbateexpressionofsuchgeneswillbepresentinat-risk,“pro-inflammatory”obesepopulations.Insupportofthisidea,recentworkidentifiesincreasedinflammatorysignaturesintheuterineenvironmentofobesefemalerats,whichleadstoweightgainandmetabolicconsequencesforoffspring(Shankaretal.,2011).Thedetailseffectorepigeneticcontributiontobodycompositionandfatdistributioninhumansarenotwellunderstoodandwillrequirefurtherin-vestigationinclinicalstudiesandanimalmodelsystems.Moreurgently,basedonourpublishedandpreliminarydataandotherpub-lisheddatadiscussedhere,wespeculatethatsurgical,dietary,andexercisein-terventionsmaybeinsufficienttoensuresustainedweightlossforobese,morbidlyobese,andsuperobesepatientsifkeygenesimportantforenergymetabolismhavebecomeepigeneticallymodifiedorreprogrammedinawaythatresistswhole-bodyreturntohealthyBMI.Suchamechanismhasnotbeenstudiedinpatientsoranimalmodelsafterweightloss,butoffersacompellingpossibleexplanationforthepersistentfailureofthesetherapeuticinterventionsamongmanypatients.Epigenetic“correction”mightbepossiblewithdrugsthatdirectlyaffect“writers”ofhistonemethylationandacetylationmarkssuchashistonedeacetylaseinhibitors,or“readers,”suchasthesmall-moleculeBETproteininhibitors.Re-randomizationofcertainepigeneticmarksofhistoneacetylation,methylation,orofDNAmethylation,mighthelppatientstoloseweightbyencouragingkeytissuesofthebodyto“forget”theunfortunatemetabolichistoryofchronicobesity.Thus,metabolic“set-point”couldberesettoahealthyorexigenicstateandBMIwouldbeeasiertonormal-izeafterweightloss.Withoutthiskindofdruginterventiontocorrecttheepigeneticstatusquoofchronicobesity,successfulandsustained,long-termweightloss,evenafterbariatricsurgery,maywellbeimpossibleformostpatients. DisruptionCausesMetabolicallyHealthy ACKNOWLEDGMENTSWethankDr.MinamiHaraoftheUniversityofChicagoforthegenerousgiftofamouseinsulinpromoter-eGFPreporterconstruct.WealsothankCarolineApovian,BarbaraCorkey,BarbaraNikolajczyk,andMartinObinforusefuldiscussionsandvaluablesuggestions.G.V.D.issupportedbytheNationalInstitutesofHealth(R56DK090455),theBostonUniversityClinicalandTranslationalScienceInstitute(UL1-TR000157),andtwoNIH-supportedCenters:theBostonAreaDiabetesandEndocrinologyResearchCenter(P30DK057521;PI:JosephAvruch)andtheBostonNutritionObesityResearchCenter(P30DK046200;PI:SusanK.Fried).G.V.D.iscurrentlytheChairofBasicScienceSectionofTheObesitySociety,andgratefullyacknowledgestheSocietyforitssupportandpromotionofscientificinteractionsandcollaborations.REFERENCESAguilar-Salinas,C.A.,Garca,E.G.,Robles,L.,Riano,D.,Ruiz-Gomez,D.G.,GarcUlloa,A.C.,etal.(2008).Highadiponectinconcentrationsareassociatedwiththemet-abolicallyhealthyobesephenotype.TheJournalofClinicalEndocrinologyandMetabolism,4075–4079.Alberti,K.G.,Eckel,R.H.,Grundy,S.M.,Zimmet,P.Z.,Cleeman,J.I.,Donato,K.A.,etal.(2009).Harmonizingthemetabolicsyndrome:AjointinterimstatementoftheIn-ternationalDiabetesFederationTaskForceonEpidemiologyandPrevention;NationalHeart,Lung,andBloodInstitute;AmericanHeartAssociation;WorldHeartFederation;InternationalAtherosclerosisSociety;andInternationalAssociationfortheStudyof,1640–1645.Apovian,C.M.,Bigornia,S.,Mott,M.,Meyers,M.R.,Ulloor,J.,Gagua,M.,etal.(2008).Adiposemacrophageinfiltrationisassociatedwithinsulinresistanceandvascularendo-thelialdysfunctioninobesesubjects.Arteriosclerosis,Thrombosis,andVascularBiologyBarker,D.J.(1995).Fetaloriginsofcoronaryheartdisease.BritishMedicalJournalBarker,D.J.,Osmond,C.,Golding,J.,Kuh,D.,&Wadsworth,M.E.(1989).Growthinutero,bloodpressureinchildhoodandadultlife,andmortalityfromcardiovasculardis-BritishMedicalJournal,654–657.Bastard,J.P.,Maachi,M.,Lagathu,C.,Kim,M.J.,Caron,M.,Vidal,H.,etal.(2006).Recentadvancesintherelationshipbetweenobesity,inflammation,andinsulinresis-EuropeanCytokineNetwork,4–12.Beck,S.,Hanson,I.,Kelly,A.,Pappin,D.J.C.,&Trowsdale,J.(1992).AhomologueoftheDrosophilafemalesterilehomeotic)geneintheclassIIregionofthehumanMHC.,203–210.Belkina,A.C.,Blanton,W.,Wang,F.,Liu,H.,&Denis,G.V.(2010).WholebodyBrd2deficiencyprotectsobesemicefrominsulinresistancebycreatingalowinflammatory,S58.Belkina,A.C.,&Denis,G.V.(2010).Obesitygenesandinsulinresistance.CurrentOpinioninEndocrinology,Diabetes,andObesity,472–477.Belkina,A.C.,&Denis,G.V.(2012).BETdomainco-regulatorsinobesity,inflammationandcancer.NatureReviews.Cancer,465–477.Belkina,A.C.,Nikolajczyk,B.S.,&Denis,G.V.(2013).BETproteinfunctionisrequiredforinflammation:Brd2geneticdisruptionandBETinhibitorJQ1impairmacrophageinflammatoryresponses.JournalofImmunology,Inpress.Bernstein,B.E.,Meissner,A.,&Lander,E.S.(2007).Themammalianepigenome.,669–681. FangnianWangetal. Bernstein,B.E.,Mikkelsen,T.S.,Xie,X.,Kamal,M.,Huebert,D.J.,Cuff,J.,etal.(2006).Abivalentchromatinstructuremarkskeydevelopmentalgenesinembryonicstemcells.,315–326.Bhandare,R.,Schug,J.,LeLay,J.,Fox,A.,Smirnova,O.,Liu,C.,etal.(2010).Genome-wideanalysisofhistonemodificationsinhumanpancreaticislets.GenomeResearchher,M.(2010).Thedistinctionofmetabolically‘healthy’from‘unhealthy’obeseindi-CurrentOpinioninLipidology,38–43.Bonora,E.,Willeit,J.,Kiechl,S.,Oberhollenzer,F.,Egger,G.,Bonadonna,R.,etal.(1991).U-shapedandJ-shapedrelationshipsbetweenseruminsulinandcoronaryheartdiseaseinthegeneralpopulation.TheBruneckStudy.DiabetesCare,221–230.Burkly,L.C.,Michaelson,J.S.,Hahm,K.,Jakubowski,A.,&Zheng,T.S.(2007).TWEAKingtissueremodelingbyamultifunctionalcytokine:RoleofTWEAK/Fn14pathwayinhealthanddisease.,1–16.Cai,D.,Yuan,M.,Frantz,D.F.,Melendez,P.A.,Hansen,L.,Lee,J.,etal.(2005).LocalandsystemicinsulinresistanceresultingfromhepaticactivationofIKK-betaandNF-kappaB.NatureMedicine,183–190.Calori,G.,Lattuada,G.,Piemonti,L.,Garancini,M.P.,Ragogna,F.,Villa,M.,etal.(2011).Prevalence,metabolicfeatures,andprognosisofmetabolicallyhealthyobeseItalianin-dividuals:TheCremonaStudy.DiabetesCare,210–215.Campbell,S.,Burkly,L.C.,Gao,H.,Berman,J.W.,Su,L.,Browning,B.,etal.(2006).ProinflammatoryeffectsofTweak/Fn14interactionsinglomerularmesangialcells.TheJournalofImmunology,1889–1898.Cancello,R.,Henegar,C.,Viguerie,N.,Taleb,S.,Poitou,C.,Rouault,C.,etal.(2005).Reductionofmacrophageinfiltrationandchemoattractantgeneexpressionchangesinwhiteadiposetissueofmorbidlyobesesubjectsaftersurgery-inducedweightloss.,2277–2286.CentersforDiseaseControlandPrevention(CDC)(2010).Vitalsigns:state-specificobesityprevalenceamongadults—UnitedStates,2009.MMWRMorbMortalWklyRepChacon,M.R.,Richart,C.,Gomez,J.M.,Mega,A.,Vilarrasa,N.,Fernandez-Real,J.M.,etal.(2006).ExpressionofTWEAKanditsreceptorFn14inhumansubcutaneousadiposetissue.Relationshipwithotherinflammatorycytokinesinobesity.Cytokine,129–137.Chen,J.R.,Zhang,J.,Lazarenko,O.P.,Kang,P.,Blackburn,M.L.,Ronis,M.J.,etal.(2012).Inhibitionoffetalbonedevelopmentthroughepigeneticdown-regulationofHoxA10inobeseratsfedhigh-fatdiet.TheFASEBJournal,1131–1141.Christou,N.V.,Look,D.,&MacLean,L.D.(2006).Weightgainaftershort-andlong-limbgastricbypassinpatientsfollowedforlongerthan10years.AnnalsofSurgery244,734–740.Cinti,S.,Mitchell,G.,Barbatelli,G.,Murano,I.,Ceresi,E.,Faloia,E.,etal.(2005).Adi-pocytedeathdefinesmacrophagelocalizationandfunctioninadiposetissueofobesemiceandhumans.JournalofLipidResearch,2347–2355.Cooper,W.N.,Khulan,B.,Owens,S.,Elks,C.E.,Seidel,V.,Prentice,A.M.,etal.(2012).DNAmethylationprofilingatimprintedlociafterpericonceptionalmicronutrientsup-plementationinhumans:Resultsofapilotrandomizedcontrolledtrial.Dabelea,D.(2007).ThepredispositiontoobesityanddiabetesinoffspringofdiabeticDiabetesCare(Suppl.2),S169–S174.Dabelea,D.,Hanson,R.L.,Lindsay,R.S.,Pettitt,D.J.,Imperatore,G.,Gabir,M.M.,etal.(2000).Intrauterineexposuretodiabetesconveysrisksfortype2diabetesandobesity:Astudyofdiscordantsibships.,2208–2211.Dabelea,D.,Mayer-Davis,E.J.,Lamichhane,A.P.,D’Agostino,R.B.,Jr.,Liese,A.D.,Vehik,K.S.,etal.(2008).Associationofintrauterineexposuretomaternaldiabetesand DisruptionCausesMetabolicallyHealthy obesitywithtype2diabetesinyouth:TheSEARCHcase-controlstudy.DiabetesCare,1422–1426.Dabelea,D.,&Pettitt,D.J.(2001).Intrauterinediabeticenvironmentconfersrisksfortype2diabetesmellitusandobesityintheoffspring,inadditiontogeneticsusceptibility.ofPediatricEndocrinology&Metabolism,1085–1091.Deering,T.G.,Ogihara,T.,Trace,A.P.,Maier,B.,&Mirmira,R.G.(2009).Methyl-transferaseSet7/9maintainstranscriptionandeuchromatinstructureatislet-enriched,185–193.denHoed,M.,Ekelund,U.,Brage,S.,Grontved,A.,Zhao,J.H.,Sharp,S.J.,etal.(2010).Geneticsusceptibilitytoobesityandrelatedtraitsinchildhoodandadolescence:Influenceoflociidentifiedbygenome-wideassociationstudies.Denis,G.V.(2010).Bromodomaincoactivatorsincancer,obesity,type2diabetesandin-DiscoveryMedicine,489–499.Denis,G.V.,&Green,M.R.(1996).Anovel,mitogen-activatednuclearkinaseisrelatedtodevelopmentalregulator.GenesandDevelopment,261–271.Denis,G.V.,Nikolajczyk,B.N.,&Schnitzler,G.R.(2010).Anemergingroleforbromodomain-containingproteinsinchromatinregulationandtranscriptionalcontrolofadipogenesis.FEBSLetters,3260–3268.Dhalluin,C.,Carlson,J.E.,Zeng,L.,He,C.,Aggarwal,A.K.,&Zhou,M.-M.(1999).Structureandligandofahistoneacetyltransferasebromodomain.,491–496.Digan,M.E.,Haynes,S.R.,Mozer,B.A.,Dawid,I.B.,Forquignon,F.,&Gans,M.(1986).Geneticandmolecularanalysisof,amaternaleffecthomeoticgeneinDevelopmentalBiology,161–169.Ditschuneit,H.H.,Flechtner-Mors,M.,Johnson,T.D.,&Adler,G.(1999).Metabolicandweight-losseffectsofalong-termdietaryinterventioninobesepatients.TheAmericanJournalofClinicalNutrition,198–204.Duffey,K.J.,&Popkin,B.M.(2008).High-fructosecornsyrup:Isthiswhat’sfordinner?TheAmericanJournalofClinicalNutrition,1722S–1732S.Evans-Molina,C.,Robbins,R.D.,Kono,T.,Tersey,S.A.,Vestermark,G.L.,Nunemaker,C.S.,etal.(2009).Peroxisomeproliferator-activatedreceptorgammaactivationrestoresisletfunctionindiabeticmicethroughreductionofendoplasmicreticulumstressandmaintenanceofeuchromatinstructure.MolecularandCellularBiology,2053–2067.ExecutivesummaryofthethirdreportoftheNationalCholesterolEducationProgram(NCEP)expertpanelondetection,evaluationandtreatmentofhighbloodcholesterolinadults(AdultTreatmentPanelIII).2001.JournaloftheAmericanMedicalAssociation,2486–2497.Farooqi,S.,&O’Rahilly,S.(2006).Geneticsofobesityinhumans.EndocrineReviewsFilippakopoulos,P.,Qi,J.,Picaud,S.,Shen,Y.,Smith,W.B.,Fedorov,O.,etal.(2010).SelectiveinhibitionofBETbromodomains.M.M.,Stevens,G.A.,Cowan,M.J.,Danaei,G.,Lin,J.K.,Paciorek,C.J.,etal.(2011).GlobalBurdenofMetabolicRiskFactorsofChronicDiseasesCollaboratingGroup(BodyMassIndex).National,regional,andglobaltrendsinbody-massindexsince1980:Systematicanalysisofhealthexaminationsurveysandepidemiologicalstudieswith960country-yearsand91millionparticipants.TheLancet,557–567.Florez,J.(2008).ThegeneticsinType2diabetes:Arealisticappraisalin2008.TheJournalofClinicalEndocrinologyandMetabolism,4633–4642.Francis,J.,Chakrabarti,S.K.,Garmey,J.C.,&Mirmira,R.G.(2005).Pdx-1linkshistoneH3-Lys-4methylationtoRNApolymeraseIIelongationduringactivationofinsulinTheJournalofBiologicalChemistry,36244–36253. FangnianWangetal. Frayling,T.M.,Timpson,N.J.,Weedon,M.N.,Zeggini,E.,Freathy,R.M.,Lindgren,C.M.,etal.(2007).AcommonvariantintheFTOgeneisassociatedwithbodymassindexandpredisposestochildhoodandadultobesity.,889–894.Freund,A.,Orjalo,A.V.,Desprez,P.Y.,&Campisi,J.(2010).Inflammatorynetworksduringcellularsenescence:Causesandconsequences.TrendsinMolecularMedicine,238–246.Grundy,S.M.,Cleeman,J.I.,Daniels,S.R.,Donato,K.A.,Eckel,R.H.,Franklin,B.A.,etal.(2005).Diagnosisandmanagementofthemetabolicsyndrome:AnAmericanHeartAssociation/NationalHeart,Lung,andBloodInstituteScientificStatement.,2735–2752Erratumin:Circulation112,e297,e298(2005).Hales,C.N.,Barker,D.J.,Clark,P.M.,Cox,L.J.,Fall,C.,Osmond,C.,etal.(1991).Fetalandinfantgrowthandimpairedglucosetoleranceatage64.BritishMedicalJournalHaslam,D.W.,&James,W.P.(2009).Obesity.TheLancet,1197–1209.Haynes,S.R.,Dollard,C.,Winston,F.,Beck,S.,Trowsdale,J.,&Dawid,I.B.(1992).Thebromodomain:Aconservedsequencefoundinhuman,andyeastproteins.NucleicAcidsResearch,2603.Heerwagen,M.J.,Miller,M.R.,Barbour,L.A.,&Friedman,J.E.(2010).Maternalobesityandfetalmetabolicprogramming:Afertileepigeneticsoil.AmericanJournalofPhysiology.Regulatory,IntegrativeandComparativePhysiology,R711–R722.Horn,P.J.,&Peterson,C.L.(2001).Thebromodomain:AregulatorofATP-dependentchromatinremodeling?FrontiersinBioscience,D1019–D1023.Hossain,P.,Kawar,B.,&ElNahas,M.(2007).Obesityanddiabetesinthedevelopingworld—Agrowingchallenge.TheNewEnglandJournalofMedicine,213–215.Hotamisligil,G.S.,Shargill,N.S.,&Spiegelman,B.M.(1993).Adiposeexpressionoftumornecrosisfactor-:Directroleinobesity-linkedinsulinresistance.,87–91.Jaenisch,R.,&Bird,A.(2003).Epigeneticregulationofgeneexpression:Howthegenomeintegratesintrinsicandenvironmentalsignals.NatureGenetics(Suppl.),245–254.Jagannathan,M.,Hasturk,H.,Liang,Y.,Shin,H.,Hetzel,J.T.,Kantarci,A.,etal.(2009).TLRcross-talkspecificallyregulatescytokineproductionbyBcellsfromchronicinflam-matorydiseasepatients.TheJournalofImmunology,7461–7470.Jagannathan,M.,McDonnell,M.,Liang,Y.,Hasturk,H.,Hetzel,J.,Rubin,D.,etal.(2010).Toll-likereceptorsregulateBcellcytokineproductioninpatientswithdiabetes.,1461–1471.Jeanmougin,F.,Wurtz,J.-M.,LeDouarin,B.,Chambon,P.,&Losson,R.(1997).Thebromodomainrevisited.TrendsinBiochemicalSciences,151–153.Kahn,S.E.,Zinman,B.,Haffner,S.M.,O’Neill,M.C.,Kravitz,B.G.,Yu,D.,etal.(2006).ObesityisamajordeterminantoftheassociationofC-reactiveproteinlevelsandthemetabolicsyndromeintype2diabetes.,2357–2364.Kanno,T.,Kanno,Y.,Siegel,R.M.,Jang,M.K.,Lenardo,M.J.,&Ozato,K.(2004).Selectiverecognitionofacetylatedhistonesbybromodomainproteinsvisualizedinliving,33–43.Karelis,A.D.,Faraj,M.,Bastard,J.P.,St-Pierre,D.H.,Brochu,M.,Prud’homme,D.,etal.(2005).ThemetabolicallyhealthybutobeseindividualpresentsafavorableinflammationTheJournalofClinicalEndocrinologyandMetabolism,4145–4150.Kern,P.A.(1997).PotentialroleofTNFalphaandlipoproteinlipaseascandidategenesforTheJournalofNutrition,1917S–1922S.Kern,P.A.,Ranganathan,S.,Li,C.,Wood,L.,&Ranganathan,G.(2001).Adiposetissuetumornecrosisfactorandinterleukin-6expressioninhumanobesityandinsulinresis-AmericanJournalofPhysiology.EndocrinologyandMetabolism,E745–E751.Khan,T.,Muise,E.S.,Iyengar,P.,Wang,Z.V.,Chandalia,M.,Abate,N.,etal.(2009).Metabolicdysregulationandadiposetissuefibrosis:RoleofcollagenVI.MolecularandCellularBiology,1575–1591. DisruptionCausesMetabolicallyHealthy Kim,S.J.,Nian,C.,&McIntosh,C.H.(2009).Glucose-dependentinsulinotropicpolypep-tideandglucagon-likepeptide-1modulatebeta-cellchromatinstructure.TheJournalofBiologicalChemistry,12896–12904.Kim,J.Y.,vandeWall,E.,Laplante,M.,Azzara,A.,Trujillo,M.E.,Hofmann,S.M.,etal.(2007).Obesity-associatedimprovementsinmetabolicprofilethroughexpansionofad-iposetissue.TheJournalofClinicalInvestigation,2621–2637.Kintscher,U.,Hartge,M.,Hess,K.,Foryst-Ludwig,A.,Clemenz,M.,Wabitsch,M.,etal.(2008).T-lymphocyteinfiltrationinvisceraladiposetissue:Aprimaryeventinadiposetissueinflammationandthedevelopmentofobesity-mediatedinsulinresistance.sclerosis,Thrombosis,andVascularBiology,1304–1310.Klannemark,M.,Orho,M.,Langin,D.,Laurell,H.,Holm,C.,Reynisdottir,S.,etal.(1998).Theputativeroleofthehormone-sensitivelipasegeneinthepathogenesisofTypeIIdiabetesmellitusandabdominalobesity.,1516–1522.ting,N.,Fasshauer,M.,Dietrich,A.,Kovacs,P.,Schon,M.R.,Kern,M.,etal.(2010).Insulin-sensitiveobesity.AmericanJournalofPhysiology.EndocrinologyandMetabolismKyle,U.G.,&Pichard,C.(2006).TheDutchFamineof1944–1945:Apathophysiologicalmodeloflong-termconsequencesofwastingdisease.CurrentOpinioninClinicalNutritionandMetabolicCare,388–394.Lee,K.(2009).Metabolicallyobesebutnormalweight(MONW)andmetabolicallyhealthybutobese(MHO)phenotypesinKoreans:Characteristicsandhealthbehaviors.PacificJournalofClinicalNutrition,280–284.Lefebvre,A.M.,Laville,M.,Vega,N.,Riou,J.P.,vanGaal,L.,Auwerx,J.,etal.(1998).Depot-specificdifferencesinadiposetissuegeneexpressioninleanandobesesubjects.,98–103.Leibel,R.L.(2008).Energyin,energyout,andtheeffectsofobesity-relatedgenes.TheNewEnglandJournalofMedicine,2603–2604.LeRoy,G.,Rickards,B.,&Flint,S.J.(2008).ThedoublebromodomainproteinsBrd2andBrd3couplehistoneacetylationtotranscription.MolecularCell,51–60.Levin,B.E.,&Govek,E.(1998).Gestationalobesityaccentuatesobesityinobesity-proneTheAmericanJournalofPhysiology,R1374–R1379.Li,B.,Carey,M.,&Workman,J.L.(2007).Theroleofchromatinduringtranscription.,707–719.Li,H.,Mittal,A.,Paul,P.K.,Kumar,M.,Srivastava,D.S.,Tyagi,S.C.,etal.(2009).Tumornecrosisfactor-relatedweakinducerofapoptosisaugmentsmatrixmetalloproteinase9(MMP-9)productioninskeletalmusclethroughtheactivationofNuclearFactor-inducingkinaseandp38mitogen-activatedproteinkinase.TheJournalofBiologicalChem-,4439–4450.Lin,Y.J.,Umehara,T.,Inoue,M.,Saito,K.,Kigawa,T.,Jang,M.K.,etal.(2008).Solutionstructureoftheextraterminaldomainofthebromodomain-containingproteinBRD4.ProteinScience,2174–2179.Maes,H.H.,Neale,M.C.,&Eaves,L.J.(1997).Geneticandenvironmentalfactorsinrel-ativebodyweightandhumanadiposity.BehaviorGenetics,325–351.Magro,D.O.,Geloneze,B.,Delfini,R.,Pareja,B.C.,Callejas,F.,&Pareja,J.C.(2008).regainaftergastricbypass:A5-yearprospectivestudy.ObesitySurgery,648–651.Mahdi,H.,Fisher,B.A.,Kallberg,H.,Plant,D.,Malmstrom,V.,Ronnelid,J.,etal.(2009).Specificinteractionbetweengenotype,smokingandautoimmunitytocitrullinatedalpha-enolaseintheetiologyofrheumatoidarthritis.NatureGenetics,1319–1324.nez,J.A.,Cordero,P.,Campion,J.,&Milagro,F.I.(2012).Interplayofearly-lifenu-tritionalprogrammingonobesity,inflammationandepigeneticoutcomes.TheProceed-ingsoftheNutritionSociety,276–283. FangnianWangetal. Matthews,D.R.,Hosker,J.P.,Rudenski,A.S.,Naylor,B.A.,Treacher,D.F.,&Turner,R.C.(1985).Homeostasismodelassessment:Insulinresistanceand-cellfunctionfromfastingplasmaglucoseandinsulinconcentrationsinman.Diabetologia,412–419.McDonnell,M.E.,Ganley-Leal,L.M.,Mehta,A.,Bigornia,S.J.,Mott,M.,Rehman,Q.,etal.(2012).Blymphocytesinhumansubcutaneousadiposecrown-likestructures.sity(SilverSpring),1372–1378.McGillicuddy,F.C.,Harford,K.A.,Reynolds,C.M.,Oliver,E.,Claessens,M.,Mills,K.H.G.,etal.(2011).Lackofinterleukin-1receptorI(IL-1RI)protectsmicefromhigh-fatdiet-inducedadiposetissueinflammationcoincidentwithimprovedglu-cosehomeostasis.,1688–1698.Meigs,J.B.,Wilson,P.W.,Fox,C.S.,Vasan,R.S.,Nathan,D.M.,Sullivan,L.M.,etal.(2006).Bodymassindex,metabolicsyndrome,andriskoftype2diabetesorcardiovas-culardisease.TheJournalofClinicalEndocrinologyandMetabolism,2906–2912.Morris,B.J.,Zee,R.Y.,&Robinson,B.G.(1994).Significantrelationshipsofplasmalipidsandbodymassindexwithpolymorphismsatthelinkedlow-density-lipoproteinreceptorgeneandinsulinreceptorgeneloci(19p13.2)inessentialhypertensivepatients.Science(London,England),583–592.Muller,Y.,Abdussamad,M.,Hanson,R.,Knowler,W.C.,Bogardus,C.,&Baier,L.(2011).Variantsin/nearareassociatedwithbodymassindexinPimaIndians.(Suppl.1),A1400.Muller,S.,Filippakopoulos,P.,&Knapp,S.(2011).Bromodomainsastherapeutictargets.ExpertReviewsinMolecularMedicine,e29.Nakamura,Y.,Umehara,T.,Nakano,K.,Jang,M.K.,Shirouzu,M.,Morita,S.,etal.(2007).CrystalstructureofthehumanBRD2bromodomain:InsightsintodimerizationandrecognitionofacetylatedhistoneH4.TheJournalofBiologicalChemistryNathanielsz,P.W.,Poston,L.,&Taylor,P.D.(2007).Inuteroexposuretomaternalobesityanddiabetes:Animalmodelsthatidentifyandcharacterizeimplicationsforfuturehealth.ClinicsinPerinatology,515–526.Nicodeme,E.,Jeffrey,K.L.,Schaefer,U.,Beinke,S.,Dewell,S.,Chung,C.W.,etal.(2010).Suppressionofinflammationbyasynthetichistonemimic.Odegaard,J.I.,Ricardo-Gonzalez,R.R.,Goforth,M.H.,Morel,C.R.,Subramanian,V.,Mukundan,L.,etal.(2007).Macrophage-specificPPARgammacontrolsalternativeac-tivationandimprovesinsulinresistance.,1116–1120.Ohashi,K.,Parker,J.L.,Ouchi,N.,Higuchi,A.,Vita,J.A.,Gokce,N.,etal.(2009).Adiponectinpromotesmacrophagepolarizationtowardsananti-inflammatorypheno-TheJournalofBiologicalChemistry,6153–6160.Oppert,J.M.,Vohl,M.C.,Chagnon,M.,Dionne,F.T.,Cassard-Doulcier,A.M.,Ricquier,D.,etal.(1994).DNApolymorphismintheuncouplingprotein(UCP)geneandhumanbodyfat.InternationalJournalofObesityandRelatedMetabolicDisordersOrjalo,A.V.,Bhaumik,D.,Gengler,B.K.,Scott,G.K.,&Campisi,J.(2009).Cellsurface-boundIL-1alphaisanupstreamregulatorofthesenescence-associatedIL-6/IL-8-cytokinenetwork.ProceedingsoftheNationalAcademyofScienceoftheUnitedStatesof,17031–17036.Pedersen,T.A.,Kowenz-Leutz,E.,Leutz,A.,&Nerlov,C.(2001).CooperationbetweenC/EBPalphaTBP/TFIIBandSWI/SNFrecruitingdomainsisrequiredforadipocyteGenesandDevelopmentM.,&Marette,A.(2001).Targeteddisruptionofinduciblenitricoxidesynthaseprotectsagainstobesity-linkedinsulinresistanceinmuscle.NatureMedicine DisruptionCausesMetabolicallyHealthy Pickup,J.C.,&Crook,M.A.(1998).IstypeIIdiabetesmellitusadiseaseoftheinnateim-munesystem?,1241–1248.Popkin,B.M.(2007).Theworldisfat.ScientificAmerican,88–95.Popkin,B.M.,&Nielsen,S.J.(2003).Thesweeteningoftheworld’sdiet.ObesityResearch,1325–1332.Puigserver,P.,Wu,Z.,Park,C.W.,Graves,R.,Wright,M.,&Spiegelman,B.M.(1998).Acold-induciblecoactivatorofnuclearreceptorslinkedtoadaptivethermogenesis.,829–839.Rahman,S.,Sowa,M.E.,Ottinger,M.,Smith,J.A.,Shi,Y.,Harper,J.W.,etal.(2011).TheBrd4extraterminaldomainconferstranscriptionactivationindependentofpTEFbbyrecruitingmultipleproteins,includingNSD3.MolecularandCellularBiologyRavussin,E.(1995).Metabolicdifferencesandthedevelopmentofobesity.(Suppl.3),12–14.Reynisdottir,S.,Ellerfeldt,K.,Wahrenberg,H.,Lithell,H.,&Arner,P.(1994).Multiplelipolysisdefectsintheinsulinresistance(metabolic)syndrome.TheJournalofClinical,2590–2599.Ricquier,D.,Casteilla,L.,&Bouillaud,F.(1991).Molecularstudiesoftheuncouplingpro-TheFASEBJournal,2237–2242.le,M.,&Groop,L.(2009).Geneticdissectionoftype2diabetes.MolecularandCellularEndocrinology,10–17.Romano,M.,Guagnano,M.T.,Pacini,G.,Vigneri,S.,Falco,A.,Marinopiccoli,M.,etal.(2003).Associationofinflammationmarkerswithimpairedinsulinsensitivityandcoagulativeactivationinobesehealthywomen.TheJournalofClinicalEndocrinologyandMetabolism,5321–5326.Saghizadeh,M.,Ong,J.M.,Garvey,W.T.,Henry,R.R.,&Kern,P.A.(1996).Theex-pressionofTNFalphabyhumanmuscle.Relationshiptoinsulinresistance.TheJournalofClinicalInvestigation,1111–1116.Samuelsson,A.M.,Matthews,P.A.,Argenton,M.,Christie,M.R.,McConnell,J.M.,Jansen,E.H.,etal.(2008).Diet-inducedobesityinfemalemiceleadstooffspringhy-perphagia,adiposity,hypertension,andinsulinresistance:Anovelmurinemodelofde-velopmentalprogramming.,383–392.Sanchez,R.,&Zhou,M.-M.(2009).Theroleofhumanbromodomainsinchromatinbi-ologyandgenetranscription.CurrentOpinioninDrugDiscoveryandDevelopmentSchneck,L.,Valenti,C.,Amsterdam,D.,Friedland,J.,Adachi,M.,&Volk,B.W.(1970).PrenataldiagnosisofTay–Sachsdisease.TheLancet,582–584.Shankar,K.,Harrell,A.,Liu,X.,Gilchrist,J.M.,Ronis,M.J.,&Badger,T.M.(2008).Maternalobesityatconceptionprogramsobesityintheoffspring.AmericanJournalofPhysiology.Regulatory,IntegrativeandComparativePhysiology,R528–R538.Shankar,K.,Zhong,Y.,Kang,P.,Lau,F.,Blackburn,M.L.,Chen,J.R.,etal.(2011).Maternalobesitypromotesaproinflammatorysignatureinratuterusandblastocyst.S.,Kelly,T.K.,&Jones,P.A.(2010).Epigeneticsincancer.Shaw,J.E.,Sicree,R.A.,&Zimmet,P.Z.(2010).Globalestimatesoftheprevalenceofdiabetesfor2010and2030.DiabetesResearchandClinicalPractice,4–14.Shoelson,S.E.,Herrero,L.,&Naaz,A.(2007).Obesity,inflammationandinsulinresistance.,2169–2180.Shoelson,S.E.,Lee,J.,&Goldfine,A.B.(2006).Inflammationandinsulinresistance.JournalofClinicalInvestigation,1793–1801. FangnianWangetal. Silventoinen,K.,Rokholm,B.,Kaprio,J.,&Sørensen,T.I.(2010).Thegeneticandenvi-ronmentalinfluencesonchildhoodobesity:AsystematicreviewoftwinandadoptionInternationalJournalofObesity,29–40.Sims,E.A.H.(2001).Aretherepersonswhoareobese,butmetabolicallyhealthy?,1499–1504.Stich,V.,Harant,I.,DeGlisezinski,I.,Crampes,F.,Berlan,M.,Kunesova,M.,etal.(1997).Adiposetissuelipolysisandhormone-sensitivelipaseexpressionduringvery-low-caloriedietinobesefemaleidenticaltwins.TheJournalofClinicalEndocrinologyandMetabolism,739–744.Succurro,E.,Marini,M.A.,Frontoni,S.,Hribal,M.L.,Andreozzi,F.,Lauro,R.,etal.(2008).Insulinsecretioninmetabolicallyobese,butnormalweight,andinmetabolicallyhealthybutobeseindividuals.Obesity(SilverSpring),1881–1886.Umehara,T.,Nakamura,Y.,Jang,M.K.,Nakano,K.,Tanaka,A.,Ozato,K.,etal.(2010).StructuralbasisforacetylatedhistoneH4recognitionbythehumanBRD2TheJournalofBiologicalChemistry,7610–7618.Uysal,K.T.,Wiesbrock,S.M.,Marino,M.W.,&Hotamisligil,G.S.(1997).Protectionfromobesity-inducedinsulinresistanceinmicelackingTNF-alphafunction.,610–614.Vidal-Puig,A.J.,Considine,R.V.,Jimenez-Linan,M.,Werman,A.,Pories,W.J.,Caro,J.F.,etal.(1997).Peroxisomeproliferator-activatedreceptorgeneexpressioninhumantissues.Effectsofobesity,weightloss,andregulationbyinsulinandglucocor-TheJournalofClinicalInvestigation,2416–2422.Walston,J.,Silver,K.,Bogardus,C.,Knowler,W.C.,Celi,F.S.,Austin,S.,etal.(1995).Timeofonsetofnon-insulin-dependentdiabetesmellitusandgeneticvariationinthebeta3-adrenergic-receptorgene.TheNewEnglandJournalofMedicine,343–347.Wang,F.,Liu,H.,Blanton,W.P.,Belkina,A.,LeBrasseur,N.K.,&Denis,G.V.(2009).Brd2disruptioninmicecausessevereobesitywithouttype2diabetes.TheBiochemical,71–83.Waterland,R.A.,Travisano,M.,Tahiliani,K.G.,Rached,M.T.,&Mirza,S.(2008).Methyldonorsupplementationpreventstransgenerationalamplificationofobesity.nationalJournalofObesity,1373–1379.Weisberg,S.P.,McCann,D.,Desai,M.,Rosenbaum,M.,Leibel,R.L.,&Ferrante,A.W.,Jr.(2003).Obesityisassociatedwithmacrophageaccumulationinad-iposetissue.TheJournalofClinicalInvestigation,1796–1808.Wild,S.,Roglic,G.,Green,A.,Sicree,R.,&King,H.(2004).Globalprevalenceofdiabetes:Estimatesfortheyear2000andprojectionsfor2030.DiabetesCare,1047–1053.Wildman,R.P.,Muntner,P.,Reynolds,K.,McGinn,A.P.,Rajpathak,S.,Wylie-Rosett,J.,etal.(2008).Theobesewithoutcardiometabolicriskfactorclusteringandthenormalweightwithcardiometabolicriskfactorclustering:Prevalenceandcorrelatesof2phenotypesamongtheUSpopulation(NHANES1999-2004).ArchivesofInternal,1617–1624.Winston,F.,&Allis,C.D.(1999).Thebromodomain:Achromatin-targetingmodule?NatureStructuralBiology,601–604.Xu,H.,Barnes,G.T.,Yang,Q.,Tan,G.,Yang,D.,Chou,C.J.,etal.(2003).Chronicinflammationinfatplaysacrucialroleinthedevelopmentofobesity-relatedinsulinre-TheJournalofClinicalInvestigation,1821–1830.Zhao,J.,Bradfield,J.P.,Li,M.,Wang,K.,Zhang,H.,Kim,C.E.,etal.(2009).Theroleofidentifiedingenome-wideassociationstudiesinthedetermina-tionofpediatricBMI.Obesity(SilverSpring),2254–2257. DisruptionCausesMetabolicallyHealthy