Childhood Obesity.docx
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Childhood Obesity.docx
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ChildhoodObesity
ChildhoodObesity:
ARoleforGutMicrobiota?
MarinaSanchez,ShirinPanahiandAngeloTremblay *
DepartmentofKinesiology,FacultyofMedicine,LavalUniversity,Québec,QCG1V0A6,Canada
*
Authortowhomcorrespondenceshouldbeaddressed;Tel.+1-418-656-7294;Fax:
+1-418-656-2441.
AcademicEditor:
AndrewP.Hills
Received:
27October2014/Accepted:
12December2014/Published:
23December2014
Abstract
:
Obesityisaseriouspublichealthissueaffectingbothchildrenandadults.Preventionandmanagementofobesityisproposedtobegininchildhoodwhenenvironmentalfactorsexertalong-termeffectontheriskforobesityinadulthood.Thus,identifyingmodifiablefactorsmayhelptoreducethisrisk.Recentevidencesuggeststhatgutmicrobiotaisinvolvedinthecontrolofbodyweight,energyhomeostasisandinflammationandthus,playsaroleinthepathophysiologyofobesity.Prebioticsandprobioticsareofinterestbecausetheyhavebeenshowntoalterthecompositionofgutmicrobiotaandtoaffectfoodintakeandappetite,bodyweightandcompositionandmetabolicfunctionsthroughgastrointestinalpathwaysandmodulationofthegutbacterialcommunity.Asshowninthisreview,prebioticsandprobioticshavephysiologicfunctionsthatcontributetochangesinthecompositionofgutmicrobiota,maintenanceofahealthybodyweightandcontroloffactorsassociatedwithchildhoodobesitythroughtheireffectsonmechanismscontrollingfoodintake,fatstorageandalterationsingutmicrobiota.
Keywords:
childhoodobesity;gutmicrobiota;prebiotics;probiotics;bodyweight;composition
1.Introduction
Theprevalenceofobesityhasincreasedsteadilyoverthepast25years,affectingbothadultsandchildrenworldwide.Approximately60%ofadultsand30%ofchildreninCanadaareconsideredoverweightorobese[1].Obesityisphysiologicallydescribedasexcessbodyfatresultingfromalong-termpositiveenergybalance.Thisisamajorconcernasobesechildrenarehighlypronetobecomingobeseadultsandaretherefore,athighriskofdevelopingsevereco-morbiditiessuchasmetabolicsyndrome,type2diabetesandcardiovasculardisease[2].Preventionandmanagementofobesityisproposedtobegininchildhood[3].Itiswellestablishedthatpronenesstoobesitydependsonacomplexinterplaybetweennumerousfactorsthataresubjectedtobothgeneticandenvironmentalinfluences.Mostoftherelevantliteratureemphasizesthatchildhoodobesityisexplainedbysuboptimalmacronutrientcompositionofthedietandinsufficientphysicalactivity;however,recentresearchhasdocumentedthesignificantimpactofmorediscretefactorssuchasshortsleepduration[4],lowdietarycalciumintake[5],inadequatefeedingbehaviors[6]andgutmicrobiota[7].
Sincethehumangenomehasbeenrelativelystableovercenturies,itisgenerallyconsideredthatthecurrentobesityepidemiccanbeprimarilyattributedtofactorsassociatedwithamodernlifestyle.Currentevidencerevealsthatevenifgeneticvariationdoesnotappeartobethemaindeterminantofthehighprevalenceofchildhoodobesity,thereisevidenceforasignificantroleofgene-environmentinteractionswhereone’sgeneticprofileinfluencestheabilitytodealwiththeobesogenicimpactofsomeenvironmentalfactors[8].
Currentevidencesuggeststhatgutmicrobiotaplayaroleinmetabolicregulationandfooddigestionandavailability[9,10,11].Gutmicrobiotaisaspecificentitywithinthebodywhichhasitsowngenomewhosegenepoolismuchmoreabundantthantheoneofitshost.Thephysiologicfunctionsattributedtogutmicrobiotahaveextendedtoextraintestinaltissues,suchastheliver,brain,andadiposetissue,constructingnovelconnectionswithobesity[9]andrelateddisordersincludingtype2diabetes[12]andcardiovasculardisease[10].Thus,ithasthepotentialtomodulateenergyregulationaswellassystemicinflammationandshouldbeconsideredasabiologicalfeaturethatplaysaroleinthepathophysiologyofobesity.Althoughenergyintakemayaffectthecompositionofgutmicrobiota,theextenttowhichgutmicrobiotaplayacausalroleinthedevelopmentofobesityinchildrenandadultsisunclear.
Arolefortheconsumptionofprebioticsandprobioticsandtheirphysiologicfunctionalityinthemanagementofobesityareofinterestbecausestudieshavereportedpositiveassociationsbetweenconsumptionofprebiotics,probioticsandprobiotic-containingfoodssuchasdairyandlowerbodyweight[13,14].Additionally,severalstrainsofbacteriahavebeentestedasaprobioticapproachinexperimentalmodelsofobesityandinhumanstudiesdemonstratingadecreaseinfatmassandbodymassindex(BMI)[13,15,16,17].Prebioticsandprobioticsareofinterestbecausetheyhavebeenshowntoalterthecompositionofthegutbacterialcommunityandtoaffectfoodintakeandappetite,bodyweightandcompositionandmetabolicfunctionsthroughgastrointestinalpathwaysandmodulationofgutmicroflora[18,19,20,21].
Thefollowingprovidesareviewoftheroleofgutmicrobiotainenergybalance,differencesingutmicrobiotabetweenobeseandleanindividuals,thepossibleroleofprebioticsandprobioticsintheregulationofbodyweightandcompositionasnoveldietarysolutionsinthepreventionandmanagementofchildhoodobesityandtheirpotentialmechanismsofaction.
2.IntestinalMicrobiota
Intestinalmicrobiotahasbeensuggestedtoimpactenergybalanceinanimalsandhumans[11,22]bycontributingtoenergymetabolismfromcomponentsofthedietandplayingaroleinhowenergyisstoredandexpended[11,23].Previousresearchinanimalshasshownthattotalbodyfatwas40%higherinconventionallyraisedmicecomparedwithgerm-freemiceeventhoughtheyhadlowerfoodintake[9].Moreover,Turnbaugh etal. showedthattransplantationofgutmicrobiotafrom ob/ob micetogerm-freemiceledtoasignificantincreaseintotalbodyfatmasscomparedtogerm-freemicethatreceivedagutmicrobiotatransplantationfromleanmice[12].Thesefindingssuggestthatgutmicrobiotamayplayaroleinenergyharvestandobesityviamicrobialmodulation.
Humangutmicrobiotaiscomposedoftrillionsofbacteriathatbelongtotwopredominantbacterialdivisions:
Firmicutes and Bacteroidetes. Thesetwophylaareinvolvedinmicrobialdysbiosisandthedevelopmentofobesity.Severalstudiesinanimalsandhumanshaveshowndifferencesinthecompositionofgutmicrobiotaandenergymetabolismbetweenobeseandleanpopulations[24,25].Inastudyexaminingtherelationshipbetweenthecompositionofgutmicrobiotaandbodyfatloss,12obeseadultmenandwomenrandomlyassignedtoeitheralow-fatorlow-carbohydratedietforoneyearshowedalowernumberof Bacteroidetes andhigherratioof Firmicutes/Bacteroidetes whencomparedtolean,normalweightindividualsatbaseline[24].However,theratioreturnedtonormalinthoseindividualswhohadsuccessfulandsustainedweightloss.Inanotherrecentstudy,variationsinthefecalmicrobiotaof12leanandnineobeseindividualsduringdietsthatvariedincaloriccontent(2400kcal/day vs. 3400kcal/day)showedthatanalterednutrientloadinducedrapidchangesinthegutbacterialcommunity[26].
Thecompositionofgutmicrobiotaduringearlylifehasbeensuggestedtoinfluencedevelopmentofoverweight/obesityinchildren[27].Inastudyexaminingtheimpactofperinatalprobioticinterventiononthedevelopmentofoverweightandobesityinchildrenover10years,159womenwererandomizedtoeither Lactobacillusrhamnosus (1×101 colony-formingunits)andmaltodextrinforfourweeksbeforeexpecteddeliveryandsixmonthspostpartum[28].Itwasfoundthatearlygutmicrobiotamodulationwithprobioticsmaypreventexcessiveweightgainoverthefirstyearsoflife[28].Thismaybeonemechanismbywhichapredispositionforobesityisconferredfromthemothertotheinfantbecausethemotherinfluencestheoriginalinoculumsandsubsequentdevelopmentoftheinfantgutmicrobiota.
3.PotentialDietarySolutions
Thesymbioticcooperationbetweenthegutmicrobiotaanditshostcouldbeaffectedbyseveralfactorsincludingdietaryhabits[29],antibioticsandotherenvironmentalfactors[30,31,32].Consumerinterestisincreasingforfoodsandfoodcomponentsthatmayhelppreventortreatobesityandrelatedmetaboliccomplications;however,effectivedietarycountermeasureshavenotyetbeenestablished.Sincepharmacologicalapproachesmayleadtoadverseeffects,dietaryapproachesremainthesafestwaytoreduceobesityandimprovemetabolicfunctions,particularlyinchildren.Prebiotics,probioticsandfoodscontainingprebioticsandprobioticsarepotentialtoolsbecauseoftheirfunctionalphysiologicalproperties.Adysbiosiscreatedbyadiethighinfatorlowinfibre,forexample,isoneofthecausesofthedevelopmentofobesityandtheincreasedriskofdevelopingmetabolicdiseases[33].Severalstudiesshowthattheseeffectsontheintestinalmicrobiotaarereversiblewithimprovednutrition[33]andbytheadministrationofprebioticsandprobiotics.Consumptionofprebioticsandprobioticsselectivelychangesthecompositionofthegutmicrobiotainfavourofaspecificgenusandevenspecificstrainsinthecaseofprobiotics.
4.Prebiotics
Aprebioticisdefinedasa“non-digestiblefiberornon-digestiblefoodingredientthatbeneficiallyaffectsthehostbyselectivelystimulatingthegrowthand/oractivityofoneoralimitednumberofbacteriainthecolon”[34].Themostcommonprebioticsincludeinulinandoligosaccharides[35].Ithasbeenshownthatprebioticscanhaveapositiveeffectondisordersofthedigestivesystem[36,37],immunesystem[38],hypertens
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