shigayw372

SHORTCOMMUNICATIONJapanesemenhavelargerareasofvisceraladiposetissuethanCaucasianmeninthesamelevelsofwaistcircumferenceinapopulation-basedstudyTKadowaki1,2,ASekikawa2,KMurata3,HMaegawa4,TTakamiya2,TOkamura1,AEl-Saed2,NMiyamatsu5,DEdmundowicz6,YKita1,KSutton-Tyrrell2,LHKuller2andHUeshima11DepartmentofHealthScience,ShigaUniversityofMedicalScience,Shiga,Japan;2GraduateSchoolofPublicHealth,UniversityofPittsburgh,PA,USA;3DepartmentofRadiology,ShigaUniversityofMedicalScience,Shiga,Japan;4DepartmentofMedicine,ShigaUniversityofMedicalScience,Shiga,Japan;5DepartmentofClinicalNursing,ShigaUniversityofMedicalScience,Shiga,Japanand6UniversityofPittsburghMedicalCenter,PA,USAVisceraladiposetissue(VAT)isanindependentriskfactorformetabolicandcardiovasculardisorders.
TherehasbeennostudythatdemonstrateddifferentabdominalfatdistributionbetweenAsianandCaucasianmen.
AstheJapanesearelessobesebutmoresusceptibletometabolicdisordersthanCaucasians,theymayhavelargerVATthanCaucasiansatsimilarlevelsofobesity.
WecomparedtheabdominalfatdistributionoftheJapanese(n239)andCaucasian-American(n177)menaged40–49yearsingroupsstratifiedbywaistcircumferenceinapopulation-basedsample.
WeobtainedcomputedtomographyimagesanddeterminedareasofVATandsubcutaneousadiposetissue(SAT).
WecalculatedVATtoSATratio(VSR).
TheJapanesemenhadalargerVATandVSRineachstratum,despitesubstantiallylessobesityoverall.
Inmultiethnicstudies,differenceinabdominalfatdistributionshouldbeconsideredinexploringfactorsrelatedtoobesity.
InternationalJournalofObesity(2006)30,1163–1165.
doi:10.
1038/sj.
ijo.
0803248;publishedonline31January2006Keywords:abdominaladiposetissue;visceraladiposetissue;Japanese;CaucasianVisceraladiposetissue(VAT)isanindependentriskfactorforcoronaryheartdisease(CHD),1hypertension,2type-2dia-betes,3andimpairedglucosetolerance(IGT).
4AccumulationofVATisaformofobesityrelatedtoenvironmentalfactorssuchasdietandphysicalinactivity.
5AstheJapanesearelessobesebutmoresusceptibletometabolicdisordersthanCaucasians,5theymayhavelargerVATthanCaucasiansatsimilarlevelsofobesity.
TherehavebeenreportsofracialdifferencesinabdominalfatdistributionbetweenCauca-siansandAfricans,6Hispanics,7andAsians.
8,9PreviousstudieshaveshownthatAsian-AmericanandCaucasianmenhadnosignificantdifferenceinVATamongvolunteerparticipants.
8Likewise,ameta-analysisshowednosignifi-cantdifferenceinVATbetweenJapaneseandCaucasianmen.
9Inthesestudies,VATwascomparedafteradjustingforotherfactorssuchasageandobesity.
TherehasbeennoreportdirectlycomparingVATbetweentheJapaneseandCaucasianmeninapopulation-basedsample.
Therefore,wecomparedtheabdominalfatdistributionoftheJapaneseandCaucasian-Americanmenaged40–49yearsingroupsstratifiedbywaistcircumferenceinapopulation-basedsample.
Werecruited240Americanmenaged40–49years(Caucasians:82%),randomlyselectedfromAlleghenyCounty,Pennsylvania,US,and240Japanesemenaged40–49years,randomlyselectedfromKusatsu,Shiga,Japan.
WeconfinedouranalysestoCaucasianandJapanesemen,becauseAfricanmenhavebeencomparedwithCaucasianselsewhere,6andwehadonlyonemanwhocategorizedhimselfasneitherCaucasiannorAfrican-American.
Inordertocomparetheabdominaladiposetissue(AAT)distributionatsimilarlevelsofwaistcircumference,participantswithextremelylargeorsmallwaistcircumference(beyondthelevelsofmean72(s.
d.
))wereexcludedfromthepresentanalysis.
Afterexcluding44non-Caucasian-Americansand20outliersinwaistcircumference,416(239Japaneseand177Caucasian)menwereexamined.
WaistcircumferenceReceived28February2005;revised21November2005;accepted29December2005;publishedonline31January2006Correspondence:DrTKadowaki,DepartmentofHealthScience,ShigaUniversityofMedicalScience,Seta-tsukinowa-cho,Otsu,Shiga520-2192,Japan.
E-mail:kadowaki@belle.
shiga-med.
ac.
jpInternationalJournalofObesity(2006)30,1163–1165&2006NaturePublishingGroupAllrightsreserved0307-0565/06$30.
00www.
nature.
com/ijowasmeasuredtwiceattheumbilicallevelattheendoftheexhalationphasewhiletheparticipantwasstandingupright,andthemeanofthetwomeasurementswascalculated.
AreasofthewholeAATandVATweredeterminedatthelevelbetweenthefourthandfifthlumbarvertebrae,usingcomputedtomographyimagesobtainedwiththesameapparatusateachsite(GE-ImatronC150).
Areasofsub-cutaneousadiposetissue(SAT)werecalculatedasAATminusVAT,andVATtoSATratio(VSR)wascalculatedasVAT/SAT.
Thetechnicianwasblindedtotherace/ethnicityandotheridentifiableinformationabouttheparticipantsTheintra-classcorrelationcoefficientsatourreadingcenterare0.
99forSATand0.
99forVAT.
Writteninformedconsentwasobtainedfromeachparticipant.
ThestudyprotocolwasreviewedandapprovedbytheInstitutionalReviewBoardsofUniversityofPittsburgh,US,andShigaUniversityofMedicalScience,Japan.
Westratifiedtheparticipantsintoquartilestrata(fromthelowestQ1tothehighestQ4)bywaistcircumference.
Wecomparedthemeansofcontinuousvariablesusingt-tests,andconsideredthedifferencesignificantatP-valueo0.
05intwo-tailedtests.
WeperformedstatisticalanalysesusingaStatisticalPackagefortheSocialSciences(SPSSJapanInc.
version11.
0J,Tokyo,Japan).
Table1showsAAT,SAT,VAT,andVSRineachwaiststratumandoverall.
Pearson'scorrelationcoefficientsbe-tweenwaistcircumferenceandAATwere0.
90fortheCaucasianmenand0.
92fortheJapanesemen.
TheJapanesemenhadasignificantlylargerVSRthantheCaucasianmeninallwaistcircumferencestrata.
TheJapanesemenhadasignificantlylargerVATthantheCaucasianmeninQ2andQ3.
InQ1andQ4,theJapanesemenhadalargerVAT,althoughthisdifferencewasnotstatisticallysignificant.
TheJapanesemenhadalargerVATineachstratum,despiteTable1Waistcircumference,areasofwholeabdominaladiposetissue,subcutaneousadiposetissue,visceraladiposetissue,andratioofvisceraltosubcutaneousadiposetissuemeasuredatbetween4thand5thvertebrae,accordingtoquartilegroupsofwaistcircumferenceandtotalinCaucasian-AmericanandJapanesemenaged40–49yearsCaucasianJapanesePQ1(waistcircumference:67.
95–82.
80cm)n(%ofthetotal)11(6.
2%)93(38.
9%)Age(years)45.
772.
845.
172.
80.
507Abdominaladiposetissue(cm2)111.
3723.
1105.
5736.
00.
476Subcutaneousadiposetissue(cm2)63.
7714.
752.
6719.
80.
040Visceraladiposetissue(cm2)47.
6710.
152.
9719.
10.
164Ratioofvisceraltosubcutaneousadiposetissue0.
7670.
121.
0670.
32o0.
001Q2(waistcircumference:82.
85–88.
85cm)n(%ofthetotal)29(16.
4%)74(31.
0%)Age(years)44.
972.
745.
073.
00.
771Abdominaladiposetissue(cm2)159.
0733.
2166.
7727.
00.
270Subcutaneousadiposetissue(cm2)88.
7723.
081.
8714.
60.
142Visceraladiposetissue(cm2)70.
2717.
584.
8719.
70.
001Ratioofvisceraltosubcutaneousadiposetissue0.
8470.
281.
0670.
290.
001Q3(waistcircumference:88.
90–96.
75cm)n(%ofthetotal)57(32.
2%)49(20.
5%)Age(years)45.
072.
944.
972.
70.
769Abdominaladiposetissue(cm2)201.
5737.
6210.
7723.
10.
125Subcutaneousadiposetissue(cm2)116.
0727.
0109.
0717.
10.
108Visceraladiposetissue(cm2)85.
5724.
5101.
7720.
1o0.
001Ratioofvisceraltosubcutaneousadiposetissue0.
7770.
260.
9670.
25o0.
001Q4(waistcircumference:97.
00–114.
25cm)n(%ofthetotal)80(45.
2%)23(9.
6%)Age(years)45.
173.
045.
372.
70.
757Abdominaladiposetissue(cm2)292.
8750.
4267.
6735.
40.
009Subcutaneousadiposetissue(cm2)175.
0738.
6147.
3732.
10.
001Visceraladiposetissue(cm2)117.
8734.
0120.
3726.
10.
702Ratioofvisceraltosubcutaneousadiposetissue0.
7170.
260.
8670.
290.
026Totaln(%ofthetotal)177(100%)239(100%)Age(years)45.
172.
945.
172.
80.
954Waistcircumference(cm)95.
478.
285.
378.
2o0.
001Abdominaladiposetissue(cm2)230.
2774.
6161.
6761.
4o0.
001Subcutaneousadiposetissue(cm2)134.
9750.
182.
3735.
6o0.
001Visceraladiposetissue(cm2)95.
2735.
679.
3730.
9o0.
001Ratioofvisceraltosubcutaneousadiposetissue0.
7570.
261.
0270.
30o0.
001LargervisceralfatinJapanesethanCaucasianmenTKadowakietal1164InternationalJournalofObesitysignificantlysmallerwaistcircumference,AAT,SAT,andVATthantheCaucasianmenoverall.
Inthewaistcircumferencestratification,ahigherproportionoftheJapanesemenwasinthelowerquartiles(Q1andQ2),whereasahigherproportionoftheCaucasianmenwasinhigherquartiles(Q3andQ4).
Inthisstudy,wedemonstratedthattheJapanesemenhadlargerVATandVSRthantheCaucasianmenineverywaistcircumferencestratum.
Toourknowledge,thisisthefirstreporttocomparethedistributionofabdominaladiposetissuebetweenJapaneseandCaucasianmendirectlyinastandardizedmanner.
ThesefindingsofgreaterVATinJapanesemenmayhelpexplainthegreaterincidenceoftype2diabetesinthispopulationcomparedtoCaucasianmen.
5,10AstheJapanesehavealargerVATevenatlowerlevelsofobesity,itleadstoahigherriskthanCaucasians,becauseVATisanindependentpredictoroftype2diabetes3andIGT.
4Infact,intheDiabetesPreventionProgram,theobesityinclusioncriterionwaslowerforAsians(BMIX22kg/m2)thanotherraces(BMIX24kg/m2),11basedonthenotionthattheJapanesehavehigherriskoftype2diabetesatlowerlevelsofobesity.
10ThereasonwefailedtodemonstratesignificantVATdifferencesinQ1andQ4maybeduetoinsufficientsamplesizescausedbythefactthatwaistcircumferencedistributionwasskewedtooppositedirectionsinthetwogroups,resultinginasmallerproportionofeitherpopulationinthesestrata.
Infact,AATinQ4wassmallerintheJapanesemen,regardlessofwaistcircumferencestratificationandtheexclusionofoutliersinwaistcircumference.
ThisdifferencemaybecausedbytheCaucasianmen'snegativelyskewedwaistcircumferencedistribution.
However,wewereabletodemonstratethatthemeanvaluesofVATwerelargerintheJapanesethanCaucasianmen,andthatVSRwassignifi-cantlylargerintheJapanesethanCaucasianmeninallwaistcircumferencestrata.
Thestrengthsofourstudyare;(1)directcomparisoninastandardizedmanner;(2)randomlysampledparticipantsfromgeneralpopulations;and(3)narrowage-rangeof40–49yearsexemptingusfromageadjustment.
TherewasactuallynosignificantagedifferencebetweentheJapaneseandCaucasianmeninanystrataoroverall.
Theweaknessofourstudyisthelackofwomen.
Parketal.
8reportedlargerproportionofVATinAATinwomen,butnosignificantdifferenceinVATitself.
Theyalsoreportedapositiveinteractionbetweenageandraceinwomen.
Althoughtheyreportednointeractioninmen,asimilarinteractionmayhavebeenobservedinmenifwehadabroaderage-rangeinourstudy.
Inconclusion,JapanesemenhavelargerVATandVSRthanCaucasianmenacrossthesamelevelofwaistcircumference.
Inmultiethnicstudies,differenceinabdominalfatdistribu-tionshouldbeconsideredinexploringfactorsrelatedtoobesity.
AcknowledgementsThisresearchwassupportedbyGrant-in-aidforyoungscientists((B):16790335)andGrant-in-aid((A):13307016)bytheJapaneseMinistryofEducation,Culture,Sports,ScienceandTechnology,andNationalInstituteofHealth(1R01HL68200).
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