Pharmacometabolomic mapping of early biochemical changes induced by sertraline and placebo.

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by  Kaddurah-Daouk, R

Citation:TranslPsychiatry(2013)3,e223;doi:10.1038/tp.2012.142
&2013MacmillanPublishersLimited Allrightsreserved 2158-3188/13
www.nature.com/tp
Pharmacometabolomic mapping of early biochemical
changes induced by sertraline and placebo
RKaddurah-Daouk1,MBBogdanov2,WRWikoff3,HZhu1,SHBoyle1,EChurchill1,ZWang4,AJRush5,RRKrishnan1,5,
EPickering6,MDelnomdedieu7andOFiehn3
Inthisstudy,wecharacterizedearlybiochemicalchangesassociatedwithsertralineandplaceboadministrationandchanges
associatedwithareductionindepressivesymptomsinpatientswithmajordepressivedisorder(MDD).MDDpatientsreceived
sertraline or placebo in a double-blind 4-week trial; baseline, 1 week, and 4 weeks serum samples were profiled using a gas
chromatographytimeofflightmassspectrometrymetabolomicsplatform.IntermediatesofTCAandureacycles,fattyacidsand
intermediates of lipid biosynthesis, amino acids, sugars and gut-derived metabolites were changed after 1 and 4 weeks of
treatment.Someofthechangeswerecommontothesertraline-andplacebo-treatedgroups.Changesafter4weeksoftreatment
inbothgroupsweremoreextensive.PathwayanalysisinthesertralinegroupsuggestedaneffectofdrugonABCandsolute
transporters, fatty acid receptors and transporters, G signaling molecules and regulation of lipid metabolism. Correlation
betweenbiochemicalchangesandtreatmentoutcomesinthesertralinegroupsuggestedastrongassociationwithchangesin
levelsofbranchedchainaminoacids(BCAAs),lowerBCAAslevelscorrelatedwithbettertreatmentoutcomes;pathwayanalysis
inthisgrouprevealedthatmethionineandtyrosinecorrelatedwithBCAAs.Lowerlevelsoflacticacid,higherlevelsofTCA/urea
cycle intermediates, and 3-hydroxybutanoic acid correlated with better treatment outcomes inplacebo group. Results of this
studyindicatethatbiochemicalchangesinducedbydrugcontinuetoevolveover4weeksoftreatmentandthatmightexplain
partiallydelayedresponse.Responsetodrugandresponsetoplacebosharecommonpathwaysbutsomepathwaysaremore
affectedbydrugtreatment.BCAAsseemtobeimplicatedinmechanismsofrecoveryfromadepressedstatefollowingsertraline
treatment.
TranslationalPsychiatry(2013)3,e223;doi:10.1038/tp.2012.142;publishedonline22January2013
Introduction
arenotwelldefined.Responsetocurrenttherapiesintreating
Majordepressivedisorder(MDD)isacommonandpotentially MDDvariesconsiderably,with40%ofpatientsnotresponding
life-threateningpsychiatricillnessthatisasignificantcauseof and60%notremittingafteraninitialtrialoftherapy.19Boththe
disability worldwide.1 Selective serotonin (5-HT) reuptake delayed onset of antidepressant therapeutic action and the
inhibitors(SSRIs)arethemajorclassofantidepressantsfor variability in the response prevent clinicians from predicting
thetreatmentofMDD.AntidepressanteffectsofSSRIsresult whether an antidepressant is going to work for a particular
from inhibition of presynaptic 5-HT transporter, followed patient. The detailed molecular mechanisms underlying
by changes in 5-HT neurotransmission and secondary variationintreatmentresponseindepressionandthegenetic
changesinotherneurotransmittersystems,suchascatecho- and biochemical basis remain unknown although numerous
lamines,2–5neurotransmitteraminoacids6–10andacetylcho- studiesimplicatethenorepinephrineand5-HTsystems.20–23
line.11ItwasshownthatSSRIsinducedelayedtranscriptional The placebo effect adds complexity, as 30–40% of MDD
andtranslationalchangesthatmediatemolecularandcellular patientsrespondtoplacebothroughmechanismsthatarenot
neuroplasticity.12–14 Different antidepressants, including yetunderstood.24,25Furtherinsightsintothemechanismsof
SSRIs,followingtheirchronicadministrationhavebeenfound responsetoplacebovsresponsetomedicationsareneeded
toincreasebiomarkersforenergymetabolism.15–18 andanabilitytoidentifyearlyonwhomightbearesponderto
The onset of antidepressant therapeutic action typically placebo can stream line clinical trials. Development of
does not occur until at least 2–4 weeks of treatment; biomarkers that can predict early on no response should
mechanismsunderlyingthisdelayedeffectofantidepressants havegreatclinicalutility.
remain largely unknown and the biochemical changes that Metabolomicsenablestheidentificationandquantification
happenoverthefirst4weeksthatleadtotherapeuticbenefit of hundreds to thousands of compounds that can report on
1DepartmentofPsychiatryandBehavioralSciences,DukeUniversity,Durham,NC,USA;2DepartmentofNeurologyandNeuroscienceWeillCornellMedicalCollege,
NewYork,NY,USA;3UCDavisGenomeCenter,UniversityofCalifornia,Davis,NC,USA;4DepartmentofStatisticsandBioinformaticsResearchCenter,NorthCarolina
StateUniversity,Raleigh,NC,USA;5Duke-NUSGraduateMedicalSchool,Singapore;6PfizerGlobalR&D,ClinicalResearchStatistics,Groton,CT,USAand7Pfizer
GlobalR&D,NeuroscienceClinicalResearch,Groton,CT,USA
Correspondence:DrRKaddurah-Daouk,DukeUniversityMedicalCenter,Box3903,Durham,NC27710,USA.
E-mail: rima.kaddurahdaouk.duke.edu or O Fiehn, Metabolomics Research and Core Laboratories UC Davis Genome Center, Room 1314þ1315, First Floor,
451HealthSciDriveDavis,CA95616,USA
Keywords:depression;metabotype;metabolomics;pharmacometabolomics;personalizedmedicine;subclassificationofdisease
Received3May2012;revised9October2012;accepted15November2012
Earlybiochemicalchangesinducedbysertralineandplacebo
RKaddurah-Daouketal
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changes in biochemical pathways and should provide novel GC-TOF mass spectrometry. Data were collected as
insights into the complex metabolic mechanisms of disease described in Trupp et al.33 Briefly, the study design was
and drug effects.26,27 Metabolomics provides powerful tools entered into the SetupX database.34 Samples were ali-
for characterization of complex phenotypes involving endo- quotted and maintained at (cid:2)801C until use, at which point
genous and exogenous mechanisms and for studies of 30ml of samples were extracted and derivatized with
complex diseases, such as depression. We have started to methoxyamine and MSTFA to trimethylsilation. Fatty acid
applymetabolomicstoolstomapglobalplasmabiochemical methylestersinternalstandardswereincludedinthesample.
changesindepressivesubjectsinremissionandinmechan- One microliter of sample was injected using a Gerstel liner
isms involved in response to SSRIs. In prior studies we exchange system onto an Agilent 6890 gas chromatograph
identifiedperturbationsinlipidmetabolism,dicarboxylicfatty (SantaClara,CA,USA)interfacedtoaLecoPegasusIVtime
acids, branched chain and other amino acids, including of flight mass (TOF) spectrometer. Data were processed
GABA,aswellasinketonebodiesinplasmaofsubjectswith usingBinBase35andcompoundspectraandretentiontimes
MDD.28,29InastudybyJietal.,30weusedapharmacome- were matched against the Fiehn laboratory library or
tabolomics-informed pharmacogenomic research strategy NIST05.36 Intensities from all identified metabolites were
andidentifiedthatglycineandasingle-nucleotidepolymorph- summed and this value was used for data normalization.
ism (SNP) in the glycine dehydrogenase gene were asso- Thesedatawereusedforstatisticalanalysis.
ciated with response to escitalopram treatment. Merging
pharmacometabolomicswithpharmacogenomicsusing‘1000 Statisticalmethods
Genomes’ SNP imputation, we provided additional insights Metabolic signatures of sertraline and placebo (univariate
about selective serotonin reuptake inhibitor response.31 We analysis). Paired t-tests were used to determine which
also demonstrated that metabolic profiles prior to treatment metabolites changed significantly from baseline to week 1
could help distinguish responders from non-responders to and to week 4. These analyses were conducted separately
sertralineandplacebo.32 for the sertraline and placebo groups. A significant t-test
In this current study, a hypothesis-generating metabolo- indicates that a metabolite is changing differently in the two
micsapproachwasusedtomapglobalbiochemicalchanges groups.Todeterminewhich metaboliteschanged differently
inducedby1weekand4weekstreatmentwithsertralineand betweenthesertralineandplacebogroups,wecompared1-
placebo. We also correlated biochemical changes and weekchangescoresand4-weekchangescoresbetweenthe
treatmentoutcomesat1and4weeksasafirststeptowards two groups using t-tests for independent groups. Metabolite
determiningwhichbiochemicalchangescouldbeassociated values were log transformed before data analysis.
withthedelayedresponsetosertralinetreatment. Q-values37werecalculatedtocontrolforfalsediscoveryrate.
Methods Correlation with response analysis. Pearson correlation
analysis was used to examine associations of changes in
Study design and patients. Study participants were out- metabolite levels with concurrent changes in depressive
patients, 18–65 years of age, from a randomized, double- symptoms. Analyses were conducted separately for 1- and
blind, flexible dosing, placebo-controlled study performed at 4-week change. Correlations of the sertraline group and
12 clinical sites. Patients had a primary diagnosis of non- placebo group were compared using the two-sample Z-test
psychotic MDD by DSM-IV criteria, with symptoms of after hyperbolic tangent transformation. For these tests,
depression present for at least 1 month prior to screening, Q-values37werecalculatedforcontrollingthefalsediscovery
and a total baseline score 422 on the 17-item Hamilton rate.
Rating Scale for Depression (HAMD )30 at screening. The
17
full exclusion criteria for patients enrolled in the study was Response-pathway oriented analysis. After testing the
reported before.32 Patients were randomized to treatment marginaleffectsofmetabolites,wethenaimedtoidentifysets
(oraladministration)witheithersertralineorplaceboataratio ofmetaboliteswithgroupeffectsonthedrugresponsethrough
of 1:1. Sertraline dosing was started at 50mg per day at the following steps. First,anindividually significant metabolite
baseline(week0),withdoseincreasedupto100mgperday waschosenbasedontheaforementionedmarginalcorrelation
at week 1 and up to 150mg per day at week 2, as seen analysis; second, a small subset of metabolites of strong
needed by the treating clinician. The primary outcome marginal correlations with the preselected metabolite was
measure was the HAMD score. HAMD scores were identified; third, a principal component regression (PCR)
17 17
determined and serum samples were collected at baseline analysis was used to regress the drug response on several
(before treatment started), 1 week and at 4 weeks after principal components. These principal components are linear
treatment;thesampleswerecollectedfromfastingsubjects. combinations of the subset of metabolites and therefore
Acompletelistoftheinclusionandexclusioncriteriausedin representthegroupeffectofthesubset.
thisstudy,subjectsmedications,havebeendescribedinour
previousreport.32Briefly,nopsychotropicmedicationswere Pathway enrichment and network modeling. Pathways and
used by the participants. The study protocol was developed networks were analyzed using multiple approaches. Meta-
in accordance with the principles of the Declaration of Mapp38 was used to calculate metabolic networks, which
Helsinki. All patients provided written informed consent. were displayed using Cytoscape. MetaMapp uses KEGG
The study was sponsored and monitored by Pfizer (Groton, reaction pairs to build a metabolic network and then adds
CT,USA).Eachsite’sIRBapprovedandoversawthestudy. non-mappedcompoundsviaTanimotosimilarity.39
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Results Four-week treatment with sertraline. Biochemical changes
following 4-week treatment with sertraline were far more
Sample characteristics. The sertraline and placebo extensive than changes seen after 1 week of treatment
groups did not differ significantly in age (44±11.4 years (Table 1). Prominent effects were found on levels of fatty
vs 40±12.7 years, P¼0.12), gender (29/43 (69%) acids (linoleic, palmitic, arachidonic, oleic, palmitoleic and
female vs 32/46 (70%) female, P¼0.83) or race (34/43 heptadecanoicacidsallshoweddecreases)andglycerol,as
(79%)whitevs34/46(74%)white,P¼0.57).Theresponse well as changes in metabolites within the TCA and urea
rate was slightly higher for sertraline than for placebo, but cycles (decreases in ornithine, citrulline and increase in
this difference was not statistically significant (26/43 (60%) aconitic acid). Other changes included metabolites from the
vs 23/46 (50%)) responders for sertraline and placebo purine pathway (xanthine decreased), one carbon metabo-
groups, respectively. lism (cysteine increased), tryptophan (5-methoxytryptamine
decreasedandindole-3-aceticacidincreased)andaketone
body (3-hydroxybutanoic acid decreased). With Q-values
Metabolicsignaturesofsertralineafter1and4weeksof
cutoff controlled at 0.1, significant changes were decreased
treatment. A GC-TOF metabolomics platform was used to
levels of linoleic, arachidonic and palmitic acids, and of
semiquantitatively measure 348 compounds in patient
ornithine and glycerol. A metabolic network reconstruction
serum. Of these, 143 were known compounds, 17 com-
that highlights the metabolites changed after 4-week treat-
pounds were identified by spectral matching to the NIST
mentwith sertralineisshowninFigure1b.
libraryand188wereunknown.
Pathway enrichment analysis for 4-week treatment with
sertralineisshowninTable2.Severalpathwaysinvolvedin
One-week treatment with sertraline. Several metabolites signalingwereenrichedinthisanalysisincludingtransmem-
were changed following 1 week of treatment with sertraline; brane transporters of small molecules, signaling by GPCR,
they included intermediates of TCA cycle, sugars and fattyacidreceptorsandtransporters.
metabolites involved in fatty acid biosynthesis
(Supplementary Table 1). All metabolites except glycerol Metabolic signatures of placebo after 1 and 4 weeks of
showed an increase in concentration over this period. treatment
However, with Q-value cutoff set at 0.1 none of these One-weektreatment. Metabolitesthatchangedafter1-week
changes was found to be significant. A metabolic network treatmentwithplaceboareshowninSupplementaryTable1.
reconstructionhighlightingthemetabolitesthatchangedafter Changes included amino acids homoserine and aspartate,
1weekofsertraline isshowninFigure1a. one metabolite, xanthine, from the purine pathway, and the
Figure1 Compoundschangingsignificantly(Po0.05)inthefirst(a,lefttop)andfourth(b,righttop)weekofsertralinetreatmentup(green)ordown(red)areshownas
enlargednodes.Placebotreatmentinthefirstweek(c,leftbottom)andfourthweek(d,rightbottom)isalsoshown.Allcompoundsthatweremeasuredintheexperimentare
shown.GraylinesindicatenetworkconnectionsbaseduponstructuralsimilarityandboldbluelinesindicateKEGGreactionpairs.
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Table1 Metabolicchanges(Po0.05)after4-weektreatmentwithsertralineandplacebo
Metabolite Sertraline P Q Metabolite Placebo P Q
t-value Percent t-value Percent
change change
Linoleicacid (cid:2)3.791 (cid:2)20.471 0.001 0.036 Elaidicacid (cid:2)5.259 (cid:2)30.801 5.500E(cid:2)06 0.003
Ornithine (cid:2)3.788 (cid:2)18.435 0.001 0.036 Fructose 4.213 487.726 1.443E(cid:2)04 0.014
Glycerol (cid:2)3.597 (cid:2)15.845 0.001 0.052 Hippuricacid 4.389 331.668 8.420E(cid:2)05 0.014
Arachidonicacidisomer (cid:2)3.306 (cid:2)16.947 0.002 0.088 Linoleicacid (cid:2)4.175 (cid:2)22.794 1.617E(cid:2)04 0.014
Palmiticacid (cid:2)3.444 (cid:2)14.788 0.002 0.072 Oleicacid (cid:2)4.206 (cid:2)21.281 1.472E(cid:2)04 0.014
Arachidonicacid (cid:2)3.123 (cid:2)15.713 0.004 0.113 Palmitoleicacid (cid:2)4.520 (cid:2)24.734 5.620E(cid:2)05 0.014
Hippuricacid 3.031 268.553 0.005 0.115 Methioninesulfoxide 3.082 77.910 0.004 0.113
Oleicacid (cid:2)3.024 (cid:2)0.299 0.005 0.115 Propane-1,3-diolNIST (cid:2)3.099 (cid:2)11.241 0.004 0.113
Aconiticacid 2.912 26.214 0.006 0.122 a-Ketoglutaricacid (cid:2)2.997 (cid:2)11.514 0.005 0.115
Cystine 2.667 327.080 0.012 0.161 Palmiticacid (cid:2)2.978 (cid:2)10.948 0.005 0.115
Palmitoleicacid (cid:2)2.597 131.426 0.014 0.172 Homoserine (cid:2)2.879 (cid:2)4.833 0.006 0.122
5-Methoxytryptamine (cid:2)2.530 425.326 0.016 0.184 Inulobiose 2.835 88.022 0.007 0.127
Xanthine (cid:2)2.538 (cid:2)8.746 0.016 0.184 Myristicacid (cid:2)2.843 (cid:2)9.520 0.007 0.127
Myristicacid (cid:2)2.480 (cid:2)8.007 0.018 0.190 Cytidine-50-diphosphate (cid:2)2.590 1.726 0.013 0.172
Indole-3-acetate 2.462 21.503 0.019 0.191 Glycerol (cid:2)2.535 (cid:2)7.201 0.015 0.183
Heptadecanoicacid (cid:2)2.358 (cid:2)7.089 0.024 0.201 Arabitol 2.479 15.601 0.018 0.190
3-Hydroxybutanoicacid (cid:2)2.345 33.418 0.025 0.201 Creatinine 2.473 148.690 0.018 0.190
Xylitol 2.197 163.060 0.035 0.228 Hydroxylamine (cid:2)2.481 (cid:2)8.192 0.018 0.190
HydroxycarbamateNIST 2.152 298.069 0.039 0.228 2-Deoxytetronicacid 2.434 31.055 0.020 0.193
Asparagines 2.132 53.085 0.040 0.228 Histidine 2.393 59.236 0.022 0.200
Uricacid (cid:2)2.111 (cid:2)6.143 0.042 0.230 Proline 2.375 30.962 0.023 0.201
Succinicacid (cid:2)2.067 (cid:2)5.740 0.046 0.235 Glutamine 2.330 82.385 0.025 0.201
Maltose 2.302 171.497 0.027 0.204
3-Hydroxybutanoicacid (cid:2)2.245 9.976 0.031 0.213
Pseudouridine (cid:2)2.158 (cid:2)5.284 0.037 0.228
2-DeoxyerythritolNIST 2.131 133.213 0.039 0.228
GABA 2.133 139.734 0.039 0.228
Glutamicacid 2.098 1264.390 0.042 0.230
Sucrose 2.107 597.169 0.042 0.230
Hydrocinnamicacid (cid:2)2.089 (cid:2)6.049 0.043 0.230
Xanthine (cid:2)2.092 (cid:2)5.011 0.043 0.230
Quinicacid 2.070 210.924 0.045 0.233
Oxoproline (cid:2)2.050 (cid:2)5.221 0.047 0.235
Benzylalcohol (cid:2)2.043 17.474 0.048 0.235
SignificantP-valuesareinbold.
Table2 Pathwayenrichmentanalysisoftheeffectofsertralineexposurefrombaselinetoweek4
Pathwayname PT OV Metabolites P Q
Transmembranetransportofsmallmolecules R 9 170(192) 1.21E(cid:2)06 1.51E(cid:2)03
SignalingbyGPCR R 7 84(93) 1.30E(cid:2)06 1.51E(cid:2)03
Signaltransduction R 7 89(98) 1.93E(cid:2)06 1.51E(cid:2)03
RegulationoflipidmetabolismbyPPAR-a R 3 5(5) 3.60E(cid:2)06 2.12E(cid:2)03
SLC-mediatedtransmembranetransport R 8 147(165) 4.85E(cid:2)06 2.28E(cid:2)03
Freefattyacidreceptors R 4 19(23) 8.34E(cid:2)06 3.27E(cid:2)03
Transportoffattyacids R 3 9(9) 2.97E(cid:2)05 9.96E(cid:2)03
GPCRligandbinding R 5 66(75) 9.26E(cid:2)05 0.027
Ga(q)signalingevents R 4 38(43) 1.45E(cid:2)04 0.038
Nucleotidemetabolism W 3 16(17) 1.91E(cid:2)04 0.045
Fattyacid,triacylglycerolandketonebodymetabolism R 5 83(89) 2.78E(cid:2)04 0.059
Glucosehomeostasis W 3 21(21) 4.44E(cid:2)04 0.087
ArachidonateproductionfromDAG R 2 5(5) 5.32E(cid:2)04 0.096
ClassA/1(Rhodopsin-likereceptors) R 4 56(64) 6.62E(cid:2)04 0.111
Abbreviations:PCR,principalcomponentregression;PT,sourceofpathway;R,Reactome;W,Wikipathways;OV,numberofoverlappingmetabolites;P,P-value
calculatedformetabolites;Q,Q-valuecalculatedformetabolitesaftercorrectionforFDR.
fatty acids linoleic, oleic and palmitoleic acids. Each treatment with placebo, compared with 1 week (Table 1).
metabolite showed a concentration decrease. However, Reductionswerefoundinlevelsoffattyacids(linoleic,oleic,
similarly to 1-week treatment with sertraline, none of these myristic and palmitoleic acids) and glycerol. Other changes
changeswassignificantwithQ-valuecutoff of0.1. included TCA cycle metabolites (decreased a-ketoglutarate,
and increased glutamine and glutamic acid), amino acids
Four-week treatment with placebo. Significantly more pro- (decreased homoserine, and increased proline, GABA and
found biochemical changes were observed after 4 weeks of glutamic acid), metabolites linked to one carbon cycle
TranslationalPsychiatry
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(increased creatinine and decreased homoserine) Table3 Correlationswithtreatmentoutcomes:correlationsbetweenbiochem-
(Figure 1d). Both xanthine from the purine pathway, and icalchangesandchangesinHam-D
the ketone body 3-hydroxybutanoic acid were decreased.
Metabolite Cor P-value
With Q-values cutoff controlled at 0.1, significant changes
werefoundforelaidic,hippuric,linoleic,oleicandpalmitoleic (a)One-weeksertraline
5-Methoxytryptamine 0.405 0.016
acidsandfructose.
Arachidonicacidisom (cid:2)0.398 0.018
Ribose 0.389 0.021
Associations of changes in metabolites with treatment Cystine 0.370 0.029
outcomes Trehalose 0.358 0.035
a-Ketoglutaricacid (cid:2)0.339 0.047
One-week treatment with sertraline. The associations
Xylose (cid:2)0.335 0.049
between changes in individual metabolites and treatment
outcomewerealsoexamined.Correlationsbetweenchanges (b)One-weekplacebo
Phosphoricacid 0.510 0.001
inindividualmetabolitesandtreatmentoutcomeasassessed
4-Hydroxyproline (cid:2)0.439 0.005
using HAMD17 scores are presented in Table 3a. Decrease Cholesterol 0.397 0.011
in 5-methoxytryptamine (5-MTPM) levels was the most Malate (cid:2)0.323 0.042
significant in association with symptoms reduction following
(c)Four-weeksertraline
1weekoftreatmentwithsertraline.Symptomsreductionwas
Valine 0.507 0.002
also associated with decrease in levels of ribose, trehalose Leucine 0.478 0.004
and cystine. Increases in the levels of arachidonic and a- Lacticacid (cid:2)0.435 0.009
Pseudouridine (cid:2)0.409 0.015
ketoglutaricacidswereassociatedwithsymptomsreduction
Conduritol-b-epoxi (cid:2)0.406 0.015
after1-weeksertraline treatment. Isoleucine 0.382 0.024
MannonicacidNIST 0.380 0.024
Cystine 0.362 0.032
Four-week treatment with sertraline. After 4 weeks of
Inulobiose (cid:2)0.361 0.033
sertralinetreatment,themostsignificantchangesassociated
with symptoms reduction were decreases in the levels of (d)Four-weekplacebo
branched chain amino acids (BCAAs), valine, leucine and Lacticacid 0.383 0.015
Ribose6 (cid:2)0.371 0.018
isoleucine (Table 3c). Similarly to 1 week, at 4 weeks of
3-Hydroxybutanoicacid (cid:2)0.355 0.025
sertraline treatment symptoms reduction were associated Oxalicacid 0.346 0.029
with increase in levels of cysteine. Improvement of the HydroxycarbamateNIST 0.345 0.029
Citrulline (cid:2)0.336 0.034
symptoms after 4 weeks on sertraline was also associated
Indole-3-acetate 0.323 0.042
withincreasesinthelevelsoflacticacidandpseudouridine. 1-Monostearin 0.318 0.046
One-weektreatmentwithplacebo. After1weekoftreatment Negative correlations indicate better response with increase in metabolite;
with placebo, decrease in phosphoric acid and increases in positiveindicatesbetterresponsewithdecreaseinmetabolite.
4-hydroxyprolineandmalate(Table3b)wereassociatedwith
symptoms reduction. Changes in several metabolites within
TCA/urea cycle also correlated with changes in depression acids is warranted in studying biological mechanisms of
scores. sertraline.
Four-week treatment with placebo. Changes in lactic acid,
Discussion
sugars, oxalic acid, ketone body, indole-3-acetic acid, urea
cycleintermediatecirtrulineandalaninewereassociatedwith Recently, weconductedametabolomicsstudytodetermine
symptoms reduction at 4 weeks of placebo treatment whetherthebaselinemetabolicprofile(thatis,metabotype)of
(Table 3d). In contrast to the sertraline findings, no a patient with MDD would allow a prediction of patient’s
associationbetweenchangesinlevelsofBCAAswasnoted. response to treatment with sertraline or placebo.32 In that
study,utilizinganelectrochemistry-basedanalyticalplatform
Response-pathway oriented analysis. Since valine was that enables quantification of redox active compounds, we
foundtobethemostsignificant metaboliteshowingcorrela- foundthatmetabolitesfromphenylalanine,tryptophan,purine
tionwithresponseinthesertralinegroup,weselectedalistof and tocopherol pathways enabled separation of responders
26 metabolites (Supplementary Table 2) marginally corre- and non-responders to treatment with the SSRI or placebo.
lated with valine in sertraline group including leucine, Thecurrentstudyextendsonthesefindingsby(1)analyzing
isoleucine and tyrosine. A PCR analysis with variable differentclassesofmetabolitesusingGC-TOFmassspectro-
selection identified four principal components jointly and metry analytical platform; (2) identifying the biochemical
significantly associated with drug response. In the first changes that occur in MDD patients 1 week and 4 weeks
principal component (Supplementary Table 3), isoleucine, aftertreatmentwithsertralineorplacebo,and(3)identifying
leucine, methionine, valine and tyrosine possessed the whichchangesareassociatedwithareductionindepressive
largest weights. Thus, this metabolite set characterized by symptomsafter1and4weeksoftreatmentwithsertralineor
major amino acids explored the possible relationship placebo.
between amino acids, their transport and function, and Severalmetabolitesfrommultiplepathwayswerechanged
depression, suggesting that further investigation of amino insertraline-andplacebo-treatedsubjects.Inbothsertraline-
TranslationalPsychiatry
Earlybiochemicalchangesinducedbysertralineandplacebo
RKaddurah-Daouketal
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and placebo-treated patients, the larger effects were glycolysisinmice,52and5-HThadstimulatoryandinhibitory
observedafter4weeksoftreatmentcomparedwith1week. effects on glycogen synthesis in hepatocytes mediated by
Multiple mechanisms could account for the biochemical 5-HT1/2Aand5-HT2Breceptors,respectively.53
changes observed in this study. Progression of the disease We also analyzed associations between changes in
itself,aswellasbehavioralchanges(forexample,changesin individual metabolites and treatment outcome. After 1 week
diet) associated with improvement of the symptoms after ofsertralinetreatment,thedecreasein5-methoxytryptamine
treatment,couldexplainsomeoftheeffectssuchaschanges andincreasesinarachidonicacidanda-ketoglutaratelevels
infattyacidsandindicesofenergymetabolism.Thus,itwas were the most significant in association with symptoms
suggestedthatplasmalevelsoflinoleicacidmayserveasa reduction.Associationofdecreasein5-MTPMwithsymptoms
possible biomarker for residual depression and anxiety in reductionsuggestspotentialroleofmethoxyindolebranchof
older people with previous depression;40 it was also shown the tryptophan pathway in recovery form depressed state;
earlier that increased dietary intake of oleic acid was currently we are investigating different branches of the
associated with reduced risk of severe depressed mood pathway in the effects of SSRIs. Changes in the levels of
amongwomenwhileincreaseddietaryintakeoflinoleicacid arachidoniclevelsmostlikelyreflectincreaseintheactivityin
wasassociatedwithincreasedriskofseveredepressedmood phospholipase A2, resulting from increased 5-HT levels at
amongmen.41Itwasrecentlyfoundthatomega-3augmenta- earlier time point.44,45 Association of increased levels of a-
tion of SSRI citalopram treatment produced a significantly ketoglutaratewithsymptomsreductionisnotclear;however,
greaterreductioninHAM-Dscorescomparedwithcitalopram it may be related to the activation of energy metabolism
treatment alone.42 In a yeast model, sertraline has been followingSSRItreatment.Insupportofthismechanismisthe
shown to inhibit phospholipases A1 and D and activates observation that improvement of symptoms at 4 weeks of
phospholipase A2.43 It is thus possible, if the effect on treatment with sertraline was associated with decreased
phospholipases is similar in mammalian systems, that the levelsoflacticacid.Themostsignificantchangesassociated
changes in fatty acids observed in this study could be the with symptoms reduction after 4 weeks of treatment with
result of sertraline inhibition and/or activation of specific sertraline were decreases in the levels of BCAAs, valine,
phospholipases. It was also shown in primary cultures of leucine and isoleucine. In our previous study, we have
mouseastrocytes thatchronic SSRIstreatment upregulates demonstrated that higher levels of leucine and isoleucine
calcium-dependentphospholipaseA2(PLA2),whichreleases were associated with depression.29 BCAAs have well-
arachidonic acid from the membrane-bound phospholi- established anabolic effects on protein metabolism that
pids.44,45 Additional mechanism, involving PLA2 activation involves activation of mTOR pathway. In this respect, it is
and increased release of arachidonic acid following SSRIs particularly interesting that antidepressant effect of NMDA
could involve membrane phospholipids remodeling and receptorantagonistketamineresultsfromactivationofmTOR
changes in signal transduction pathways.46,47 The changes pathway involving BCAAs.54 In a recent study, Webhofer
noted in fatty acids in the placebo group are of interest and etal.18foundthatinmicevaline,leucineandisoleucinelevels
couldreflectchangesinfattyacidbiosynthesisordegradation wereincreasedafterchronictreatmentwithSSRIparoxetine.
asdisease progresses. It can alsobe common towhat was Detailed mapping of effects of SSRIs, as well as of other
observedinthesertralinegroup. antidepressants, on metabolism in animals and in humans
Several studies implicated impairment of energy metabo- should be compared at a more detailed level to enable
lismpathwaysinbothpathogenesisofdepressionandeffects translationalresearch.
ofantidepressants.Inananimalmodelofdepression,levels Of interest, there were several metabolites that closely
of aconitate hydratase and pyruvate dehydrogenase were correlated with changes in BCAAs and these included
found to be regulated in opposite directions by stress and methionine and tyrosine. Methionine and the methionine
antidepressant drug treatment, thus representing molecular cycle are closely linked to the folate cycle, to one carbon
correlatesofbothvulnerabilitytodepressionandresponseto metabolism and to methylation processes that have been
drug.48 Chronic administration of different antidepressants, implicatedindepression.
including SSRIs, was associated with increased levels of While there is strong evidence that MDD is influenced by
biomarkers for energy metabolism, such as activity of brain inheritance,55 GWA studies for possible genetic factors that
creatinekinase,ofmitochondrialrespiratorychaincomplexes contribute to MDD risk, as well as GWA studies for genes
IIandIV,andofcitratesynthaseandsuccinatedehydrogen- associated with SSRI response in MDD patients, have
ase.17,49,50Recentlyinananimalmodelsignificantchangesin provided somewhat disappointing results.56,57 However, it
amino-acidmetabolismrelatedtoenergymetabolismviaTCA wasdemonstratedthattheSNPintheABCB1geneencoding
cycle,andincreasedlevelsofglucose,glucose-6-phosphate ATP-binding cassette, subfamily B (MDR/TAP), member 1
andfructose-6-phosphatefollowingchronicparoxetinetreat- (ABCB1)transporterproteinexpressedintheendothelialcells
ment were found.18 Additional mechanisms related to the oftheblood–brainbarrier,isassociatedwithseverityofMDD
observedchangesinenergymetabolismfollowingsertraline and its response to citalopram and escitaloppram.58,59
treatmentcouldberelatedtotheeffectsof5-HTonglucose Recently,inGWAstudyKohlietal.60identifiedtheSNPina
metabolism and glycolysis. It was demonstrated that 5-HT gene encoding a neuron-specific neutral amino-acid trans-
stimulates glucose uptake in skeletal muscle and activates porter, SLC6A15, as an MDD risk gene. While the exact
skeletalmuscle6-phosphofructo-1-kinaseactivityinadose- function of the SLC6A15 SNP is not well understood, from
responsethrough5-HT2Areceptors.51Recently,itwasfound both human and animal studies, it is known that SLC6A15
that 5-HT through 5-HT2A receptors controls hepatic belongstothesolutecarrier6(SLC6)genefamily,whichalso
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