Melatonin(N-acetyl-5-methoxytryptamine)isanaturallyoccurringhormonefoundinanimals,plants,andmicrobes. Inhumans,melatoninisproducedprimarilybythe pinealgland,locatedinthecenterofthebrain.Melatoninformspartofthesystemthatregulatesthe sleep-wakecycle bychemicallycausingdrowsinessandloweringthebodytemperature. Productionofmelatoninbythepinealglandisinhibitedbylightandpermittedbydarkness. Secretionofmelatonin,aswellasitslevelintheblood,peaksinthemiddleofthenightandgraduallyfallsduringthesecondhalfofthenight,withnormalvariationsintimingaccordingtoanindividual’s chronotype.(1,2) MelatoninisalsoimportantforitsABIlitytoscavengefreerADIcalsandtoregulatetheactivityandexpressionofantioxidantandpro-oxidantenzymes.(3,4,5)

Inhumanplasma61-85%ofmelatoninisweaklyboundtoproteins,andthereisacloserelationshipbetweencirculatingfreeandsalivarymelatoninlevels.(6)Melatoninenterssalivafrombloodeitherbypassivediffusionoractivetransport.(7) Melatoninismeasurableinsaliva,andtheacrophasesofsalivaandplasmamelatoninrhythmsaresignificantlycorrelated.(8,9) Plasmaandsalivarymelatoninconcentrationsincreasewhenmovingfromasupinetoastandingposition,anddecreasewhenthesepositionsarereversed,duetochangesinplasmavolume.(10) Inflammatoryprocessessuchasperiodontitistriggeranincreaseinplasmamelatonin,whichthenincreasesmelatoninlevelsintheoralcavity,whereitmayincreaseantioxidantprotection.(11)​
 

MelatoninandtheEndogenousClock

Duetoastrongcorrelationwithserummelatoninconcentrations,analysisofsalivarymelatonineffectivelyenablesresearcherstodesignnon-invasivestudiesthatassesscircadiantimingandevaluatethedegreeofcircadianphaseabnormalitiesinassociationwithmajordiseases,conditions,admiNISTrationofpharmaceuticalcompounds,seasonalaffectivedisorder,jet-lagandnightshiftwork,etc.Italsopertainstotheclinicalaspectofimprovingdiagnosisandtreatmentofirregularsleep-wakedisordersviachronotherapyusingexogenousmelatoninoralteredlightexposure.Researchofmelatonindysregulationaffectsmultiplebody-widesystemsandoftenresultsinchronicsleepdeficitswithsymptomsthatcanbemisdiagnosedasdepression,attentiondeficithyperactivitydisorder,fibromyalgia,orchronicfatigue.

DLMO&MelatoninOnsetAnalysis

WithsalivaasaBIOLOGicalsample,researcherscannon-invasivelymonitormelatoninlevelswithoutanovernightsleepclinicstay(polysomnogram).Thiseliminatestherhythmperturbationcausedbyaclinicalsleepcenterlaboratory,canbeperformedin4-6hrs(asopposedto24hrs),andofferstheconvenienceofcollectingsamplesathome.SalivaryDLMOisdeterminedbymeasuringsalivarymelatoninlevelsoverseveraltime-pointspriortoandjustafterhabitualsleeptime.Calculatingthetimethatthenocturnalmelatoninconcentrationissignificantlyelevatedfromdaytimesamples(+/-2deviationsfrombaselinelevels)-DMLOisthemostsensitiveanddirectindexforidentifyinganindividual’sbiorhythmwhichmaybeentrained(synchronized)toa24hrlight/darkcycleorcanbeinafree-runningstate.AmisalignedDMLOmayindicatedelayedsleepphasesyndrome(DSPS)oradvancedsleepphasedisorder(ASPD)anditsrelationshiptovariousmetabolicconditions,diseases,disordersandgeneticandenvironmentalcomponentsareofsignificantinterestincurrentresearch.

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