Whenweeatmaybejustasimportantaswhatweeat.Anewstudyshowsthatmicethateatwhentheyshouldbesleepinggainmoreweightthanmicethateatatnormalhours.Anotherstudyshedslightonwhywepackonthepoundsinthefirstplace.Whetherthesestudiestranslateintotherapiesthathelphumansbeatobesityremainstobeseen,buttheygivescientistscluesaboutthemyriadfactorsthattheymusttakeintoaccount. Observationsofovernightworkershaveshownthateatingatnightdisruptsmetabolismandthehormonesthatsignalwe’resated.Butnoonehaddonecontrolledstudiesonthisconnectionuntilnow.BiologistFredTurekofNorthwesternUniversityinEvanston,Illinois,andgraduatestudentDeannaArbleexaminedthelinkbetweenahigh-fatdietandwhattimeofdaymiceeat.Acontrolgroupofsixnocturnalmiceatetheirpellets(60％fatbycalories,mostlylard)duringthenight.Anothergroupofsixatethesamemealduringtheday,Tureksays,whichdisruptstheircircadianrhythm—thebody’snormal24-hourcycle. After6weeks,theoff-schedulemiceweighedalmost20％morethanthecontrols,TurekandArblereporttodayin?Obesity,supportingtheideathatconsumingcalorieswhenyoushouldbesleepingisharmful.TurekandArbleacknowledgethatthedisruptedmiceateatadmoreandwereatadmoresluggish,butthedifferencescouldnotaccountforalloftheweightgain. Inthesecondstudy,adifferentteamofresearchersinvestigatedthelinkbetweenweightandtheimmunesystem.Hundredsofgenesseemtoaffecttheaccumulationoffat,butonethathelpsprotectusfrominfectionmighthelpusloseweightwithlittleeffort,biochemistAlanSaltieloftheUniversityofMichigan,AnnArbor,andcolleaguessuggesttodayin?Cell.Theresearcherstestedmeweight-addingabilitiesofaproteincalledIKK∈,whichislinkedwithobesity,diabetes,andchronic,low-1evelinflammation.For3months,theteamfedsixmicemissingIKK∈genesadietofhigh-fatchow. BecauseIKKE’smainjobisimmunedefense,Saltiel’steamdidn’texpecttofindweightdifferencesbetweenknockoutmiceandcontrols.Buttheknockoutmicedidgainsignificantlyless.Bestofall,thegirththeanimalsdidaddwaslessharmfultotheiroverallhealth.“Theknockoutmicedon’tgainasmuchweightbutalsodon’tgetdiabetes,don’tgetinsulinresistance,anddon’tgetaccumulationoflipidsontheliver,”Saltielsays,allofwhichcontributetothesuiteofhealthproblemsassociatedwithbeingoverweight.SaltielcallsIKK∈“anespeciallyappealingdrugtargetforthetreatmentofmetabolicdisease.” TomManiatis,amolecularbiologistatHarvardUniversitypraisesthestudybutremainsskepticalaboutanydrugthatwouldinhibitIKK∈.Hehelpeddevelopthemiceusedintheexperimentandnotesthattheyarevulnerabletotheflu.HesuspectsthatsuppressingIKK∈mayhelppeoplewithdiabetesorobesity,“butthefirsttimetheswineflucomesalong,that’sit.” ResearchersarealsoenthusiasticaboutthecircadianrhythmpaperFrankScheet,aneuroscientistatHarvardwhostudiessleep,wasstruckthat“youcouldseesomethinghappening[tothedisruptedmice]inthefirstweekalready.That’sconsistentwithhumanstudieswherewefoundchangesinjust3days.” Together,thepaperssuggestthatthere’snosimpleanswertowhypeoplegainweight.SaysTurek,“It’sclearlynotjustcaloriesinversuscaloriesout.” Whatdoestheword“nocturnal”meaninthesecondparagraph?
A.Hungry. B.Nightly C.Healthy D.Greedy正确答案B
