Association between the FTO gene polymorphism and obesity in Brazilian adolescents from the Northeast region 夽,夽夽

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www.jped.com.br

ORIGINAL ARTICLE

Association between the FTO gene polymorphism and obesity in Brazilian adolescents from the Northeast region ^夽,夽夽

Liliane dos Santos Rodrigues

^a^,∗

, Alcione Miranda dos Santos

^b

,

Mayara Ingrid Sousa Lima

^a

, Vanda Maria Ferreira Simões

^b

, Silma Regina Pereira

^a

aUniversidadeFederaldoMaranhão(UFMA),DepartamentodeBiologia,SãoLuís,MA,Brazil

bUniversidadeFederaldoMaranhão(UFMA),DepartamentodeSaúdePública,SãoLuís,MA,Brazil

Received24February2019;accepted13May2019 Availableonline30July2019

KEYWORDS Cohort;

Bodyfat;

rs9939609 Polymorphism

Abstract

Objective: ToinvestigatetheassociationbetweentheFTOgenepolymorphismwithobesityin BrazilianadolescentsfromtheNortheastregion.

Method: Thiswasacase---controlstudywithadolescentsaged18to19years.Thecasegroup consistedof378obeseindividualsandthecontrolgroupof378non-obeseindividuals.Obesity wasmeasuredbypercentageofbodyfatusingtheairdisplacementplethysmographytechnique.

Thestudyvariablesincludeddataonsocioeconomics,demographics,lifestyle,physicalactivity, waistcircumference, waist-to-heightratio,andbody massindex.Toidentifythers9939609 polymorphismoftheFTOgene,bloodsampleswereobtainedforgenomicDNAextractionby thereal-timePCR(PolymeraseChainReaction)technique.Categoricalvariableswerecompared betweenthegroupsbythechi-squaredtest.Thenormalityoftheanthropometricmeasurements bodymassindex,waistcircumference,waist-to-heightratio,andpercentageofbodyfatwas evaluatedbytheShapiro---Wilktest.Comparisonoftheanthropometricmeasurements,stratiﬁed bythepolymorphismgenotypes,wasperformedbytheKruskal---Wallistest.TheHardy---Weinberg equilibriumwascalculated.Thesigniﬁcancelevelwassetat5%.

Results: Thevariablesgender,age,andphysicalactivityshowedsignificantdifferencesbetween thegroups(p<0.001).Thesamplesofobeseandnon-obeseadolescentswereinHardy---Weinberg equilibrium(p=0.0515).Therewasnosignificantdifferencebetweenthegenotypic(p=0.719) andallelicfrequencies(p=0.812)regardingthecaseandcontrolgroups.Whencomparingthe anthropometricmeasurementsaccordingtothegenotypes(AA,AT,andTT),nosignificantdiffer- encewasobservedforbodymassindex(p=0.337),waistcircumference(p=0.3473),percentage ofbodyfat(p=0.7096),andwaist-to-heightratio(p=0.2584).

夽 Pleasecitethisarticleas:RodriguesLS,SantosAM,LimaMI,SimõesVM,PereiraSR.AssociationbetweentheFTOgenepolymorphism andobesityinBrazilianadolescentsfromtheNortheastregion.JPediatr(RioJ).2020;96:630---7.

夽夽StudyconductedatUniversidadeFederaldoMaranhão,SãoLuís,MA,Brazil.

∗Correspondingauthor.

E-mail:lilik.beq@hotmail.com(L.S.Rodrigues).

https://doi.org/10.1016/j.jped.2019.05.006

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Conclusion: Theexcessadiposityofthestudyadolescentswasnotinﬂuencedbytheirgenotype.

4.0/).

PALAVRAS-CHAVE Coorte;

Gorduracorporal;

Polimorﬁsmo rs9939609

Relac¸ãodopolimorﬁsmodogeneFTOcomaobesidadeemadolescentesdonordeste brasileiro

Resumo

Objetivo: Investigararelac¸ãodopolimorﬁsmodogeneFTOcomobesidadeemadolescentes noNordestebrasileiro.

Método: Estudocaso-controlerealizadocomadolescentesde18a19anos.Ogrupocasofoi formadopor378indivíduosobesoseocontrolepor378nãoobesos.Obesidadefoimedidapelo percentualdegorduracorporalpelatécnicadepletismografiapordeslocamentodear.Variáveis emestudoenglobamdadossocioeconômicos,demográficos,hábitosdevida,atividadefísica, circunferênciadacintura,razãocintura-estaturaeíndicedemassacorporal.Paraidentificação dopolimorfismors9939609dogeneFTOforamobtidasamostrasdesangueparaextraçãodoDNA genômicopelatécnicadePCRemtemporeal.Variáveiscategóricasforamcomparadasentre osgrupospelotestequi-quadrado.Normalidadedasmedidasantropométricasíndicedemassa corporal,circunferênciadacintura,razãocintura-estatura epercentual degorduracorporal foramavaliadospelotesteShapiro-Wilk.Comparaçãodasmedidasantropométricas,estratifi- cadaspelosgenótiposdopolimorfismo,foirealizadapelotesteKruskall-Wallis.Calculou-seo equilíbriodeHardy-Weinberg.Níveldesignificânciaadotadode5%.

Resultados: Asvariáveissexo,idadeeatividadefísicaapresentaramdiferençassignificativas entre osgrupos (p<0,001).Asamostras dosadolescentesobesos enão obesosestavam em equilíbriodeHardy-Weinberg(p=0,0515).Nãohouvediferençasignificanteentreasfrequên- ciasgenotípicas(p=0,719)ealélicas(p=0,812)emrelaçãoaosgruposcasoecontrole.Quando comparadasasmedidasantropométricassegundo osgenótipos(AA, ATeTT),não foiobser- vadadiferençasignificantedoíndicedemassacorporal(p=0,3337),circunferênciadacintura (p=0,3473),percentualdegorduracorporal(p=0,7096)erazãocintura-estatura(p=0,2584).

Conclusão: Oexcessodeadiposidadedos adolescentesemestudo nãofoi inﬂuenciado pelo genótipo.

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Introduction

Obesity,characterizedbyanexcessiveaccumulationofbody fat, brings complications that can be often observed in increasingly youngerindividuals. Somefactors arerelated to this picture, among them environmental factors, the individual’slifestyle,differentiateddiet,andenvironmental contaminantsthatcanactasendocrinedisruptors.¹

The adolescents’ social conditions aredeﬁned accord- ingtotheenvironmentwheretheylive.²Inthissense,the dietatthisstageis highlycaloric,withingestionof ultra- processedproducts, in additiontoinadequatelife habits, suchassedentarylifestyleandexcessiveuseofelectronic equipment,whichareaspectsthatcontributetothedevel- opmentofobesity.³Additionally,thegeneticmakeupofthe individualmayalsocontributetotheonsetofobesity,espe- ciallywhenassociatedwithaninadequatelifestyle.⁴

Obesity contributes tothe onsetof non-communicable chronicdiseases(NCCDs).²AccordingtoAfmanandMüller,⁵ the NCCDs, such as type 2 diabetes mellitus (T2DM), metabolic syndrome (MS), and cardiovascular diseases (CVDs),resultfromtheseassociationsofenvironmentaland

geneticfactors,interferinginpeople’sliveswhentheyare obeseoroverweight.

Approximately 70% of obese children and adolescents tendtobecomeobeseadultsaswell.⁶Excessweightisasso- ciatedwithagradualincreaseintheriskofmorbidityand mortalityinadulthood,sinceobesityisoneoftheriskfac- torsfornoncommunicablediseasesanddisorders,beingthe maincausesofdeathinadults.

This can lead toan increased risk of premature death anddisabilityinadultlife,asinBrazil,amongadolescents (10---19years),atleastone-ﬁfthhadexcessweightand4.9%

wereobese,withhigherindicesinthemalepopulationand intheagegroupof10---11yearsold.⁷

Fromthegeneticpointofview,differentpolymorphisms havebeen described inthe literature asbeingassociated with obesity.⁸ Among these, the fat mass and obesity- associatedgene(FTO)hassingle-nucleotidepolymorphisms (SNPs) associated withthe metabolism alteration process and,therefore,theirpresencehasadirectassociationwith thestatusofobesity,overweight,andotherpathologies.⁹

ThemostofteninvestigatedFTOgenepolymorphismthat isassociatedwithobesityisrs9939609,characterizedbythe

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substitutionofTbyAinintron1.Studiesindicatethatindi- viduals whoare homozygous for the risk allele (A allele) areapproximately3kgheavierormore,andhavea1.7-fold increasedriskofbeingobesewhencomparedtothosewith homozygotesfortheTallele.¹⁰ Huntetal.¹¹demonstrated thatthisSNPis associatedwithan increasedrisk ofadult individualsdevelopingobesityandotherNCCDs.

InBrazil,Silvaetal.¹² carriedoutastudywithchildren andadolescentsfromRioGrandedoSul,withasampleof 348 children followed from birth to 8 years of age, and anotheroneconsistingof615childrenandadolescentsfrom 4to18 yearsof age. The authorsobserved that individuals with the A/A genotype had a higher Z-score for body massindex(BMI),abdominalcircumference,andskinfolds.

However, Souza et al.¹³ carried out a study with adults andchildren, also in Brazil,and observed the absenceof associationbetweentheFTOgeneandtheanthropometric measuresusedinthecomparisons.

It is evident that, for the most part, the studies that associate FTO gene polymorphisms and obesity were carried out with adult populations and in European and or Asian countries or in Brazilian regions predominantly of Europeandescent,wherepopulationsaregeneticallymore homogeneouswhencomparedthoseoftheLatinAmerican countries,whicharetypicallymixed-race.¹⁴Therefore,very oftentheresultsarenotnecessarilythesameindifferent ethnicgroupsorgroupsorganizedbyagerange.

Thus,theaimofthisstudywastoinvestigatetheasso- ciationofapolymorphismintheFTO genewithobesityin adolescentsfromthe municipality of SãoLuís, Maranhão, Brazil.

Methods

Studytype

This was a case-control study with adolescents(18 to 19 years)fromtheRPSCohortofSãoLuís,Maranhão.TheRPS cohort encompassesthe cities of Ribeirão Preto, state of São Paulo; Pelotas, state of Rio Grande do Sul; and São Luís,stateofMaranhão,whosemainobjectivewastoeval- uatethehealth ofindividualsbornin1997andtomonitor theirhealth untiladulthood. Forthat purpose, datawere collectedperiodicallyonbreastfeeding,homestimulation, mental disorders, violence, nutrition, body composition, sleep,physicalactivity,andgeneticfactors,amongothers.

Studypopulationandsample

Thestudypopulationconsistedof2515adolescents.Adoles- centswithoutinformationonthemainvariables(percentage offat,weight,height,gender,andage)wereexcludedfrom thestudy.Therefore,thepopulationconsistedof2382ado- lescents.

Thesamplesizewascalculatedconsideringa95%conﬁ- dencelevel,anda powerof 80%;theoddsratio(OR)was estimatedaprioriat2.0,withafrequencyof16%¹⁰ forthe rs9939609SNPoftheFTOgeneinindividualshomozygousfor theriskallele(A)andwitharatioofonecasetoonecon- trol.Thus,682adolescentswerenecessary,i.e.,341cases and341controls.

Adolescents with a percentage of body fat (%BF)>25%

(boys) and >30% (girls) were deﬁned as obese (cases), totaling629adolescents.Thecontrolscomprisedgirlswith

%BF≤30% and boys with %BF≤25% (n=1753). In both groups,theadolescentswererandomlyselectedconsidering theminimumsamplesizeofeachgroup,andalladolescents includedwereeligible.

The study included 782 adolescents,but there wasno ampliﬁcation in the sample of 26 adolescents, who were excluded fromthestudy.Thus,theﬁnal sample consisted of 756 adolescents,378 in the non-obese group (control) and378oftheobesegroup(case).

Socioeconomicanddemographicdata,lifehabits

The assessed socioeconomic and demographic variables were as follows: age, gender, family income, level of schooling,ethnicity/skin color, numberof peopleliving in the household, and the Brazilian Economic Classiﬁcation Criteria, marital status, separated or divorced parents, occupation, and smoking status. This information was obtained throughastructuredinterview, according tothe standardizedquestionnairesoftheRPSCohort.

The Mini International Neuropsychiatric Interview (M.I.N.I.)---Brazilian version5.0.0---DSMIVisaninterview focused onthe diagnosis of mental disorderssuch as the antisocial personality and risk of suicide; however, only information related to alcohol consumption was used.¹⁵ When asked about how frequently they consumed drinks containingalcohol, thepresent study considered as‘‘no’’

forthosewhoanswered‘‘never’’and‘‘yes’’forthosewho said they consumed alcohol ‘‘once or more than once a week.’’

The physical activity level was evaluated through the 24-h Physical Activity Recall, created from the Self- AdministeredPhysicalActivityChecklist(SAPAC),¹⁶classiﬁed assedentary,low,moderate,orhigh.¹⁷

Anthropometricandnutritionalassessment

Weight measurements (in kg) were performed using a Filizola^®(Filizola,SP,Brazil)scalecoupledtoanairdisplace- mentplethysmography(ADP)system.Theparticipantswere askedtostandbarefoot,standinguprightinthecenterofthe scale,wearingtheleastpossibleclothing,headorientedin thehorizontalFrankfurtplaneandwearingnoaccessories, toundergothemeasurementofheightincentimeters,with theaidofanAlturexata^® (Alturexata,MG,Brazil)portable stadiometer.Basedonthesedata,theBMIwascalculatedby the ratio:bodyweight(kg)/height (m²).Measurements of waistcircumference(WC)wereobtained,consistingofthe measurement(incm)atthemidpointbetweentheiliaccrest andthelastrib.Eachparticipantwasmeasuredtwice,and theﬁnalresultwastheaverageofthetwomeasurements.

Theparticipants’proportionofcentralfatbyheightwas evaluatedthroughthewaist-to-heightratio(WHtR),calcu- lated by dividing the waist circumference (cm) by height (cm).ThepointsweredeterminedaccordingtoAshwelland Hsieh,¹⁸ indicatedfor adolescentsofbothgenders,consid- eringvaluesbelow0.50tobeadequate.

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Table1 Socioeconomic,demographic,andlifestylecharacteristicsofparticipantsfromtheRibeirãoPreto,Pelotas,andSão Luís,(RPS)CohortofSãoLuís,Maranhão,Brazil,2019.

Variables Total Non-obese Obese p-Value

n % n % n %

Gender

Male 295 39.02 223 58.99 72 19.05 <0.001

Female 461 60.98 155 41.01 306 80.95

Age(years)

18 500 66.14 267 70.63 233 61.64 0.009

19 256 33.86 111 29.37 145 38.36

Ethnicity

White 166 22.05 78 20.63 88 23.47 0.585

Black 121 16.07 64 16.93 57 15.20

Mixed-race 466 61.89 236 62.43 230 61.33

Maritalstatus

Single 725 95.90 363 96.03 362 95.77 0.640

Married 8 1.06 5 1.32 3 0.79

Common-lawmarriage 23 3.04 10 2.65 13 3.44

Levelofschooling

A/FI-i 1 0.13 0 0.00 1 0.26

FI-c/FII-i 1 0.13 1 0.26 0 0.00 0.120

FII-c/M-i 239 31.61 132 34.92 107 28.31

M-c/S-i 515 68.12 245 64.81 270 71.43

Employed

No 646 85.45 323 85.45 323 85.45 1.000

Yes 110 14.55 55 14.55 55 14.55

Familyincome(minimumwages)

<1 129 17.06 72 19.05 57 15.08

1<2 213 28.17 113 29.89 100 26.46 0.118

2<3 118 15.61 57 15.08 61 16.14

3<4 75 9.92 37 9.79 38 10.05

≥4 118 15.61 60 15.87 58 15.34

Unknown 103 13.62 39 10.32 64 16.93

Separated/divorcedparents 0.610

No 393 51.98 193 51.06 200 52.91

Yes 363 48.02 185 48.94 178 47.09

CCEB

ClassA 63 8.34 27 7.16 36 9.52

ClassB 491 65.03 242 64.19 249 65.87 0.237

ClassC 199 26.36 106 28.12 93 24.60

ClassesD---E 2 0.26 2 0.53 0 0.00

Physicalactivitylevel

Sedentary 373 49.47 145 38.56 228 60.32

Low 93 12.33 49 13.03 44 11.64 <0.001

Moderate 167 22.15 101 26.86 66 17.46

High 121 16.05 81 21.54 40 10.58

Smoker

No 728 96.55 365 97.07 363 96.03 0.433

Yes 26 3.45 11 2.93 15 3.97

Alcoholconsumption

No 437 58.03 216 57.60 221 58.47 0.810

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Table1(Continued)

Variables Total Non-obese Obese p-Value

n % n % n %

Yes 316 41.97 159 42.40 157 41.53

A,illiterate;FI-I,incompleteelementaryschool;FI-c,completeelementaryschool;FII-I,incompletejuniorhigh;FII-c,completejunior high;M-I,incompletehighschool;M-c,completehighschool;S-I,incompletecollege/university;CCEB,BrazilianEconomicClassiﬁcation Criteria.p-value,signiﬁcantwhen<0.05.

Thenutritionalstatusoftheadolescentswasevaluated bythe BMI,adoptingastheclassiﬁcationcriteriathe val- ues for age and gender and the respective cutoff points proposedby theWorldHealth Organization¹⁹ for individu- alsaged10.0---19.0years;for youngindividuals olderthan 19.0years,theWorldHealthOrganizationclassiﬁcationwas followed.²⁰

Theevaluationoftotalbodyfatwasperformedusingthe ADPmethodin theCOSMEDBod Pod^® (Teprel, Porto,Por- tugal)gold standard device.The %BFwasestimated using Siri’sequation.²¹AccordingtotheclassiﬁcationbyWilliams etal.,²² boyswitha%BF>25%andgirls>30%wereconsid- eredashavingexcessweight.

FTOgenepolymorphism

Samples of 5mL of whole blood were collected fromthe cubitalveinand storedunderrefrigeration.GenomicDNA wasextracted using the DNA Blood MiniKit (Qiagen, CA, UnitedStates)usingaQIAcubeautomated extractor(Qia- gen, CA, United States), according to the manufacturer’s recommendations.Then,theywerestored ina freezerat

−20^◦Cforanindeterminateperiodinordertoavoidpossible lossofmaterialorcontamination.

A NanoDrop spectrophotometer (Termo Scientiﬁc, CA, United States), was used for the quantiﬁcation of the extracted DNA, according to the manufacturer’s instruc- tions.

Theanalysisofthers9939609SNPoftheFTOgenewas performedusingtherhAmp^TMSNPGenotypingSystem(Inte- gratedDNATechnologies,IA,UnitedStates)assayona7500 FastSystemreal-timePCRsystem(AppliedBiosystems,CA, UnitedStates).Thereagentswerepurchasedcommercially andusedaccordingtothemanufacturer’sstandards.

Statisticalanalysis

The statistical analysis was performed using the statisti- calsoftwareSTATA(StataStatisticalSoftware:Release14.

CollegeStation,TX, UnitedStates). The normalityof the anthropometric measures (BMI, WC, WHtR, and %BF) was evaluatedbytheShapiro---Wilktest.Thestudyvariablesin the case group were comparedwith those in the control group,usingthechi-squaredtest.

TheHardy---Weinbergequilibriumwascalculatedforthe geneticdata.²³TheKruskal---Wallistestwasusedtocompare the means of anthropometric measures stratiﬁed by the

differentgenotypesoftherS9939609polymorphismofthe FTOgene.Inalltests,thesigniﬁcancelevelwassetat5%.

Ethicalconsiderations

ThestudywasapprovedbytheResearchEthicsCommittee ofHospitalUniversitáriodaUniversidadeFederaldoMaran- hão (No. 1,302,489), in accordance with national health councilResolutionNo.466/2012andCNSOperationalRule No.001of2013.

Results

The totalsample consistedof461girlsand297boys,with amean ageof18.34 years.Thecase groupwascharacte- rizedby80.95%femalesubjects;61.64%wereaged18years or younger; 61.33%were mixed-race;95.77% weresingle;

71.43% were in high school or college/university; 85.45%

did not work; 26.46% had a familyincome of one totwo minimumwages;52.91%hadnon-separatedparents;65.87%

were classiﬁed as belonging to social class B. Regarding lifestyle,60.32%weresedentary,96.03%werenon-smokers, and58.47%%didnotconsumealcoholicbeverages(Table1).

In the control group, 58.99% of the individuals were males;70.63%wereaged18years;62.43%declaredthem- selves as mixed-race; 96.03% were single; 64.81% of adolescentshadﬁnishedhighschoolorwereattendingcol- lege/university;85.45% didnotwork;29.89%hadafamily incomeofonetotwominimumwagesinthemonthpriorto the interview; 51.06% hadseparated parents, and 64.19%

were in social class B. Regarding lifestyle, 49.47% were sedentary, 97.07% were nonsmokers, and 57.60% did not drinkalcohol.Onlythevariablesgender,age,andphysical activityshowedstatisticallysigniﬁcantdifferencesbetween thegroups(p<0.001;Table1).

ThecaseandthecontrolgroupswereinHardy---Weinberg equilibrium(p=0.0515).The distributionof thers9939609 polymorphism wasnotstatisticallydifferentin relationto thegenotypic(p=0.719)andallelicfrequencies(p=0.812;

Table2).

Regardingtheanthropometricmeasuresofthetotalsam- ple according to the adolescents’ genotype, there was no statistically signiﬁcant difference between the means of BMI (p=0.337), WC (p=0.343), %BF (p=0.7096), and WHtR(p=0.2584)whencomparingthedifferentgenotypes (Table3).

For comparison purposes, results from studies evalu- ating the association between obesity and the rs9939609 polymorphism ofFTO geneareshown. BMIor dual-energy

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Table2 GenotypicandallelicfrequenciesoftherS9939609polymorphismoftheFTOgeneintheRibeirãoPreto,Pelotas,and SãoLuís(RPS)CohortofSãoLuís,Maranhão,Brazil,2019.

Gene(SNP) Genotype Non-obese(%BF) Obese(%BF) p-Value^a

N:378 GF(%) N:378 GF(%)

TT 146 38.62 153 40.48

AT 181 47.88 170 44.97 0.719

FTO(rs9939609) AA 51 13.49 55 14.55

Alleles N:378 AF(%) N:378 AF(%)

T 473 62.57 480 63.16 0.812

Ag 283 37.43 280 36.84

SNP,single-nucleotidepolymorphism;%BF,percentageofbodyfat;GF,genotypicfrequency;FTO,fatmassandobesity-associatedgene;

AF,allelicfrequency,riskalleleforobesity.

a Chi-squaredtest.

Table3 Comparisonbetweenthemeansoftheanthropometricmeasuresandgenotypeinthetotalsampleofadolescentsof theRibeirãoPreto,Pelotas,andSãoLuís(RPS)CohortofSãoLuís,Maranhão,Brazil,2019(n=756).

Measure FTOrs9939609 p-Value^a

A/A A/T T/T

Mean SD Mean SD Mean SD

BMI 23.56 4.26 23.03 4.24 23.47 4.40 0.3337

WC 84.16 7.98 83.75 9.27 84.92 9.87 0.3473

%BF 26.15 11.30 25.41 11.86 26.25 11.44 0.7096

WHtR 0.50 0.05 0.50 0.05 0.51 0.06 0.2584

FTO,fatmassandobesity-associatedgene;SD,standarddeviation;BMI,bodymassindex(kg/m²);WC,waistcircumference(cm);%BF, percentageofbodyfat;WHtR,waist-to-heightratio.

a Kruskal---Wallistest.

Table4 Prevalenceofobesityandtheallelicandgenomicfrequenciesofdifferentstudies.

Typeofstudy Obeseindividuals(%) GF(%) AF(%) References

TT AT AA T A

Case---control 53.3 20.0 23.1 22.6 46.9 49.5 Pereiraetal.⁴

Cross-sectional 34.5 33.1 28.9 57.4 59.3 40.7 Reuteretal.²³

Cross-sectional 12.0 77.0 22.0 1.0 87.0 13.0 Floresetal.²⁴

Cross-sectional 35.1 74.4 23.4 2.1 86.2 13.8 Xietal.²⁵

GF,genotypicfrequency;AF,allelicfrequency.

X-ray absorptiometry (DXA) wereused asthe criterion to deﬁne obesity.Differentprevalence ratesof obesity were observed,aswellastheallelic(AF)andgenomic(GF)frequencies(Table4).

Inthisstudy,theGFoftheTTgenewashigherthanthe frequencyshowninthestudiesbyPereiraetal.⁴andReuter etal.,²⁴butlowerthanthatofthestudiesbyFloresetal.²⁵ and Xi etal.²⁶ Regarding theAT gene,the GF washigher thanthatobservedintheotherstudiesshowninTable4.The AAgeneshowedlowerfrequencywhencomparedwiththe studiesbyPereiraetal.⁴andReuteretal.,²⁴butwashigher thanthatofthestudiesbyFloresetal.²⁵ andXietal.²⁶ In relationtotheAFofT,ahigherfrequencywasfound than thatofPereiraetal.⁴andReuteretal.,²⁴andalowerAFfor theAallele.

Discussion

The rs9939609 SNPof the FTO genehas been extensively studiedinthescientificenvironment,especiallyinrelation toitsinfluence onthebody. Wahlénetal.,²⁷ studyingthe associationbetweenfatcellmetabolismandthisSNP,con- cludedthatindividuals whoareheterozygous(AT) forthis polymorphismwouldhaveagreatercapacityforlipiddeteri- orationduetoahighconcentrationofanorganiccompound calledglycerol.Anotherrelevant findingabout thisSNPis itspossibleassociationwitheatinghabits.Itisbelievedthat carriersoftheAallele,bothinhomozygousandheterozy- gousstates,wouldhaveahigherpreferenceforfattyfoods andlittlecontroltoavoidtheirconsumption.

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Inthisstudy,theanalyzedSNPwasnotassociatedwith obesity.Moreover,itisimportanttoemphasizethatBMIval- ueswerecloseinrelationtothedifferentgenotypes(AA,AT, andTT),whichmayhighlighttheabsenceofanassociation betweenthisgenotypeandBMI.

Theassociationofthispolymorphismwithobesityshows quitediverseconclusionsintheliteratureandthefrequency isquite varied, according totheassessed ethnicgroup or evenwhether thestudies arecarried outinadult populations,adolescents,orchildren.

In thestudy by Pereira etal.,⁴ aimingto evaluatethe associationbetweentheFTO,AKT1,andAKTIPgenepoly- morphisms and childhood obesity, a sample of Brazilian childrenwasstudied,consistingof195obeseand153non- obeseindividuals,butnoassociationwasfoundbetweenthe polymorphisms and obesity/overweight. According to the authors,althoughseveral variationsoftheFTO genehave been associated with obesity in populations with a Euro- peanorigin,theireffectsonotherethnicitiesremaintobe established,andtheBrazilianethnicmixingmaybeareason forthelack ofassociationbetweenthispolymorphismand obesity.

AlsoinBrazil,anotherstudy pointedtotheabsenceof associationbetweenmetabolicandanthropometricparam- etersandFTOgenepolymorphismsinasampleconsistingof childrenandadolescents.Theauthors’explanationforthis resultisassociatedtothefactthattheBrazilianpopulation ismixedandheterogeneous.¹³

However,thereareotherstudies,suchasthatofReuter etal.,²⁴ whichfoundasigniﬁcantassociationbetweenthe Aalleleof therS9939609 SNPof theFTO geneandobese and/oroverweightindividualsclassiﬁedusingtheBMIasthe mainparameter.Liuetal.²⁸foundthat,irrespectiveofthe sample’splaceof origin, in thiscase 289 young European andAfrican-Americansaged6---19years,thepresenceofat leastoneAallelewasdirectlyrelatedtothedevelopment ofobesity.

Corroborating thepresent ﬁndings,the studyby Flores etal.,²⁵conductedinMexico,showedthatinadditiontothe lackofasigniﬁcantassociationbetweengenotypeandbody compositioninschoolchildren,boththeallelicfrequencyof AandthegenotypicfrequencyofAAwerelowercompared tothe others, at 13% and 1%, respectively. However,the methodusedbytheseresearchersfortheevaluationofbody compositionwastheabsorptiometrytechniqueusingDXA.

TheuseofBMItoevaluatebodycompositionisverycom- monintheliterature.Inthisstudy,theADPtechniquewas usedtoclassifyobesity,whichisconsideredthegoldstan- dardmethod.Itshouldbenotedthatthistechniqueshows highersensitivityandismorerobust, classifyingagreater numberofindividualsasobesewhencomparedtoBMI.²⁹

Body composition varies greatly in adolescents and depends on age, gender, ethnicity, height, and sexual maturation.³⁰ As shown in Table 4, different prevalence ratesofobesityinadolescentscanbefoundintheliterature.

Thus,thedifferencesintheliteratureregardingtheassoci- ationbetweentheFTOgeneandobesitycanbeexplained bythedifferentmethodsusedtoclassifyobesityinadoles- cents.

The results of this study also indicate that the adolescents showed similar anthropometric measures (BMI, WC, WHtR, %BF), regardless of the genotype. Xi et al.²⁶

carried out a study with obese and non-obese children and adolescents from Beijing, China, in order to investi- gate theassociation between theFTO genepolymorphism (rs9939609) with WHtR, WC, %BF, BMI, systolic and dias- tolic blood pressure, and fasting glycemia, among other associatedvariables,andfoundastrongassociationofthe anthropometricmeasurementswiththepolymorphism.

Inthiscontext,itcanbeobservedhowdifferenttheﬁnd- ingscanberegardingthissubject,whichleadstodifferent interpretations.Oneofthemreferstothedifferentpreva- lenceratesoftheallelesinrelationtoeachpopulation.

The allelicfrequencies of thepresent studywere very similar,sinceinthenon-obesegrouptheywere37.43%and 62.57%,whereasintheobesegrouptheywere36.84%and 63.16%fortheAandTalleles,respectively.Forthewhole sample, thefrequencies were 37.23%for theA alleleand 62.76%fortheTallele.Thisindicatestheabsenceofapos- sible association between the allelic frequencies and the grouptowhichtheybelong,categorizedbythepercentage ofbodyfat.

Thisistheﬁrststudytoreportdataontheprevalenceof allelesofthisSNPinthepopulationoftheBrazilianNorth- east,astherearenodeﬁnedvaluesthatrepresentBrazil,so thatacomparisoncanbemadewithpopulationsfromother countriesorcontinents.

Therefore,theliteratureindicates thattheassociation of this SNP with obesity can have quite varied results, and also when compared with different anthropometric parametersforobesityclassiﬁcationorbodymassincrease indicators.Guptaetal.³¹reportthattheethniccomposition of apopulation can havea strong inﬂuence ontheallelic andgenotypicfrequenciesofpolymorphisms,leadingtothe needforstudiesthatusesimilarmethodologiesindifferent populations,aimingtovalidatetheresultswithrobustand reproducibledata.

Inthissense,asastrongpoint,thisistheﬁrststudycar- riedoutwithadolescentsfromtheBrazilianNortheast,using differentanthropometricmeasures,suchastheuseofthe ADPtechniquetoclassifythegroupsregardingobesityand, therefore,evaluate theassociationofthers9939609 polymorphism of theFTO genewithobesity. The high costto performthestudyconstitutesaweakpoint.

Theanalysisofthestudydatashowedtherewasnoasso- ciationofthers9939609polymorphismoftheFTOgenewith the developmentof obesity,northerewasanydifference between the means of BMI, WC, %BF, and WHtR with the differentgenotypes.

Thus,itissuggestedthatnewstudiesusingthesamepro- tocolshouldbeperformed,sincetherearecontroversiesin theliterature regardingthefrequency ofthisSNPinrela- tiontothestudiedethnicgroup,aswellasthediscrepancy oftheﬁndingsinrelationtotheagegroupoftheanalyzed populations.

Funding

Conselho Nacional de Desenvolvimento Científico e Tec- nológico---CNPqandFundaçãodeAmparoàPesquisae ao Desenvolvimento Científico e Tecnológico do Maranhão --- FAPEMA.

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Conﬂicts of interest

Theauthorsdeclarenoconﬂictsofinterest.

Acknowledgements

The authors are grateful to CNPq,FAPEMA, Hospital Uni- versitáriodaUFMA,totheGeneticsandMolecularBiology LaboratoryofUFMA,tothecoordinationoftheRPSCohort ConsortiumofSãoLuís,andtoalladolescentswhoagreed toparticipateinthestudy.

References

1.RibeiroCM[Dissertação]Investigaçãodaatividadedofluoreno, naftaleno,nonilfenoleprocimidona sobrea adipogêneseem culturadecélulas.Brasília:UniversidadedeBrasília;2015.

2.TeixeiraF,MascarenhasLP,SuzukiCS,SmouterL, NovelloD.

Prevalênciadefatoresantropométricosebioquímicossobreo estadonutricionaldeadolescentes.RBONE.2018;12:S1067---77.

3.ChaeSM, Yeo JY,HwangJH,Lee JH,Lim J, Kwon I.Weight controlinadolescents:focusgroupswithKoreanadolescents andtheirteachers.JPediatrNurs.2017;33:4---9.

4.PereiraPA,Alvim-SoaresAMJr,SandrimVC,LannaCM,Souza- CostaDC,BeloVA,etal.Lackofassociationbetweengenetic polymorphismofFTO,AKT1andAKTIPinchildhoodoverweight andobesity.JPediatr(RioJ).2016;92:521---7.

5.AfmanL,MüllerM.Nutrigenomics:frommolecularnutritionto preventionofdisease.JAcadNutrDiet.2006;106:569---76.

6.Reilly JJ. Childhood obesity: an overview. Child Soc.

2007;21:390---6.

7.Instituto Brasileiro de Geografia e Estatística. Pesquisa de Orçamentos Familiares 2008---2009: antropometria e estado nutricional de crianças, adolescentes e adultos no Brasil.

IBGE, Rio de Janeiro. 2010. Available from: https://

biblioteca.ibge.gov.br/visualizacao/livros/liv45419.pdf [cited 28.01.19].

8.JesusÍC,AlleLF,PercegonaCG,PurimKS,LeiteN.Relac¸ãoentre polimorﬁsmosgenéticos, lipólise,metabolismo de lipídeos e exercíciosaeróbios.PensaraPrática.2016;19.Availablefrom:

https://www.revistas.ufg.br/fef/article/view/37232 [cited 2.07.19].

9.PhaniNM,VohraM,RajeshS,AdhikariP,NagriSK,D’SouzaSC, etal. Implicationsofcritical PPAR␥2,ADIPOQand FTOgene polymorphismsintype2 diabetesand obesity-mediatedsus- ceptibilitytotype2diabetesinanIndianpopulation.MolGenet Genomics.2016;291:193---204.

10.FraylingTM,TimpsonNJ,WeedonMN,ZegginiE,FreathyRM, LindgrenCM,etal.AcommonvariantintheFTOgeneisasso- ciatedwithbodymassindexandpredisposestochildhoodand adultobesity.Science.2007;316:889---94.

11.HuntSC,StoneS,XinY,SchererCA,MagnessCL,IadonatoSP, etal. Association ofthe FTOgenewithBMI. Obesity(Silver Spring).2008;16:902---4.

12.SilvaCF,Zandoná MR,Vitolo MR, CampagnoloPD, Rotta LN, AlmeidaS,etal.Associationbetweenafrequentvariantofthe FTOgeneandanthropometricphenotypesinBrazilianchildren.

BMCMedGenet.2013;14:34.

13.SouzaNS,MeloME,FujiwaraCT,ReinhardtHL,SantosA,Cercato C,etal.rs9939609intheFTOgeneisnotrelatedtoobesityand worstmetabolicproﬁleinacohortofobeseBrazilianchildren andadolescents.Obesity.2011;19:S1---234.

14.Ramos CF, Magna LA, Mello MP, Silva R, Moura-Neto RS.

Genetic variationand relationships at six VNTR loci in two

distinctsamplepopulationsinBrazil.AnnHumBiol.2004;31:

660---8.

15.AmorimP.MiniInternationalNeuropsychiatricInterview(MINI):

validac¸ãodeentrevistabreveparadiagnósticodetranstornos mentais.RevBrasPsiquiatr.2000;22:106---15.

16.SallisJF, StrikmillerPK,HarshaDW,FeldmanHA,EhlingerS, StoneEJ,etal.Validationofinterviewer-andself-administered physical activity checklists for ﬁfthgrade students. MedSci SportsExerc.1996;28:840---51.

17.Benedetti TR, Antunes PD, Rodriguez-A˜nez CR, Mazo GZ, PetroskiEL.ReprodutibilidadeevalidadedoQuestionárioInter- nacionaldeAtividadeFísica(IPAQ)emhomensidosos.RevBras MedEsporte.2007;13:11---6.

18.AshwellM,HsiehSD.Sixreasonswhythewaist-to-heightratiois arapidandeffectiveglobalindicatorforhealthrisksofobesity andhowitsusecouldsimplifytheinternationalpublichealth messageonobesity.IntJFoodSciNutr.2005;56:303---7.

19.WHO, World Health Organization. Growth reference 5---19 years; 2007. Available from: http://www.who.

int/growthref/who2007bmiforage/en/[accessed04.01.18].

20.WHO, World Health Organization. BMI classiﬁca- tion. 2006. Available from: http://apps.who.int/bmi/

index.jsp?introPage=intro3.html[accessed03.03.18].

21.SiriWE.Bodycompositionfromﬂuidspacesanddensity:anal- ysisofmethods.TechMeasBodyCompos.1961;61:223---44.

22.WilliamsDP,GoingSB,LohmanTG,HarshaDW,SnnivasanSR, WebberLS,etal.Bodyfatnessandriskforelevatedbloodpres- sure,totalcholesterol,andserumlipoproteinratiosinchildren andadolescents.AmJPublicHealth.1992:82.

23.Rodriguez S, Gaunt TR, Day IN. Hardy---Weinberg equilibrium testingofbiologicalascertainmentforMendelianrandomization studies.AmJEpidemiol.2009;169:505---14.

24.Reuter CP, Burgos MS, Bernhard JC, Tornquist D, KlingerEI, BorgesTS,etal.Associationbetweenoverweightandobesityin schoolchildrenwithrs9939609polymorphism(FTO)andfamily historyforobesity.JPediatr.2016;92:493---8.

25.Flores K, Garcia O, Caama˜no MC, Ronquillo D, Martínez G, Rosado J, et al. The presence of rs9939609 of FTO and rs17782313ofMC4Rmay notbeassociatedwithobesity, ele- vated glucose or altered lipidproﬁle in school children of Queretaro:preliminaryanalysis.FASEBJ.2014;28:LB336.

26.XiB,ShenY,ZhangM,LiuX,ZhaoX,WuL,etal.Thecommon rs9939609variantofthefatmassandobesity-associatedgene isassociatedwithobesityriskinchildrenand adolescentsof Beijing,China.BMCMedGenet.2010;11:107.

27.WahlénK,Sjolin E,HoffstedJ.Thecommonrs9939609 gene variant of the fat mass and obesity-associated gene FTO is relatedtofatcelllipolysis.JLipidRes.2008;49:607---11.

28.LiuG,ZhuH,LagouV,GutinB,Stallmann-JorgensenIS,Treiber FA,etal.FTOvariantrs9939609isassociatedwithbodymass indexandwaistcircumference,butnotwithenergyintakeor physicalactivityinEuropean-andAfrican-Americanyouth.BMC MedGenet.2010;11:57.

29.Santos SK, Costa RM, Santos RA, Nunes KG, Santos JO, CavalcantiV.Validac¸ãopreliminardeequac¸õesantropométri- cas para a estimativa da gordura corporal em triatletas amadores.EFDeportes.com.2015:20.Availablefrom:https://

www.efdeportes.com/efd206/equacoes-antropometricas-em- triatletas-amadores.htm[cited03.07.19].

30.Vieira AC, Alvarez MM, Marins VM, Sichieri R, Veiga GV.

Desempenho de pontos de corte do índice de massa corporal de diferentes referências na predic¸ão de gordura corporal em adolescentes. Cad Saude Publica. 2006;22:

1681---90.

31.Gupta V, Vinay DG, Raﬁq S, Kranthikumar MV, Janipalli CS, Giambartolomei C,et al.Association analysisof31common polymorphismswithtype2 diabetesand itsrelatedtraitsin Indiansibpairs.Diabetologia.2012;55:349---57.