Introduction: Clozapine-induced sialorrhea (CIS) is one of the most common side effects of clozapine use, while the mechanism remains unclear. Methods: A total of 51 schizophrenia patients taking clozapine were selected. Among them, 32 had sialorrhea, and 19 had no sialorrhea. Saliva metabolites were identified using ultra-high-performance liquid chromatography-MS/MS (UHPLC-MS/MS), and the differences in saliva metabolites in each group were analyzed through qualitatively searching HMDB, KEGG, and self-built databases, combined with multivariate statistics. After further evaluation by receiver-operating characteristic curve (ROC) analysis, the screened differential metabolites were enriched and topologically analyzed. Results: The biomarkers potentially related to CIS included 37 differential metabolites involving 17 metabolic pathways, mainly histidine metabolism (p < 0.05, impact = 0.50), pyrimidine metabolism (p < 0.05, impact = 0.08), and β-alanine metabolism (p < 0.05, impact = 0.06). Conclusion: Our study indicates that histidine metabolic pathway may contribute to the mechanism of CIS.

1.
Perkovic MN, Erjavec GN, Strac DS, Uzun S, Kozumplik O, Pivac N. Theranostic biomarkers for schizophrenia. Int J Mol Sci. 2017;18(4):733.
2.
Agerbo E, Sullivan PF, Vilhjálmsson BJ, Pedersen CB, Mors O, Børglum AD, et al. Polygenic risk score, parental socioeconomic status, family history of psychiatric disorders, and the risk for schizophrenia: a Danish population-based study and meta-analysis. JAMA Psychiatry. 2015;72(7):635–41.
3.
Hasan A, Falkai P, Lehmann I, Gaebel W. Schizophrenia. Dtsch Arztebl Int. 2020;117(24):412–9.
4.
McCutcheon RA, Reis Marques T, Howes OD. Schizophrenia-an overview. JAMA Psychiatry. 2020;77(2):201–10.
5.
GBD 2016 Disease and Injury Incidence and Prevalence Collaborators. Global, regional, and national incidence, prevalence, and years lived with disability for 328 diseases and injuries for 195 countries, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016. Lancet. 2017;390(10100):1211–59.
6.
Stępnicki P, Kondej M, Kaczor AA. Current concepts and treatments of schizophrenia. Molecules. 2018;23(8):2087.
7.
Lewis SW, Barnes TR, Davies L, Murray RM, Dunn G, Hayhurst KP, et al. Randomized controlled trial of effect of prescription of clozapine versus other second-generation antipsychotic drugs in resistant schizophrenia. Schizophr Bull. 2006;32(4):715–23.
8.
Khokhar JY, Henricks AM, Sullivan EDK, Green AI. Unique effects of clozapine: a pharmacological perspective. Adv Pharmacol. 2018;82:137–62.
9.
Hodge K, Jespersen S. Side-effects and treatment with clozapine: a comparison between the views of consumers and their clinicians. Int J Ment Health Nurs. 2008;17(1):2–8.
10.
Maher S, Cunningham A, O&apos;Callaghan N, Byrne F, Mc Donald C, McInerney S, et al. Clozapine-induced hypersalivation: an estimate of prevalence, severity and impact on quality of life. Ther Adv Psychopharmacol. 2016;6(3):178–84.
11.
Chen SY, Ravindran G, Zhang Q, Kisely S, Siskind D. Treatment strategies for clozapine-induced sialorrhea: a systematic review and meta-analysis. CNS drugs. 2019;33(3):225–38.
12.
Szabadi E, Tavernor S. Hypo- and hypersalivation induced by psychoactive drugs. CNS Drugs. 1999;11(6):449–66.
13.
Cheng-Shannon J, McGough JJ, Pataki C, McCracken JT. Second-generation antipsychotic medications in children and adolescents. J Child Adolesc Psychopharmacol. 2004;14(3):372–94.
14.
Thiyagalingam S, Kulinski AE, Thorsteinsdottir B, Shindelar KL, Takahashi PY. Dysphagia in older adults. Mayo Clin Proc. 2021;96(2):488–97.
15.
Rofes L, Clavé P, Ouyang A, Scharitzer M, Pokieser P, Vilardell N, et al. Neurogenic [corrected] and oropharyngeal dysphagia. Ann N Y Acad Sci. 2013;1300:1–10.
16.
Choromańska M, Klimiuk A, Kostecka-Sochoń P, Wilczyńska K, Kwiatkowski M, Okuniewska N, et al. Antioxidant defence, oxidative stress and oxidative damage in saliva, plasma and erythrocytes of dementia patients. Can salivary AGE be a marker of dementia? Int J Mol Sci. 2017;18(10):2205.
17.
Chang YT, Chang WN, Tsai NW, Huang CC, Kung CT, Su YJ, et al. The roles of biomarkers of oxidative stress and antioxidant in Alzheimer&apos;s disease: a systematic review. Biomed Res Int. 2014;2014:182303.
18.
Fukuchi K, Li L, Hart M, Lindsey JR. Accumulation of amyloid-beta protein in exocrine glands of transgenic mice overexpressing a carboxyl terminal portion of amyloid protein precursor. Int J Exp Pathol. 2000;81(4):231–9.
19.
Bellavía S, Gallará R. Effect of photic stimuli on rat salivary glands. Role of sympathetic nervous system. Acta Odontol Latinoam. 2000;13(1):3–19.
20.
Kozaki T, Hidaka Y, Takakura JY, Kusano Y. Suppression of salivary melatonin secretion under 100-Hz flickering and non-flickering blue light. J Physiol Anthropol. 2018;37(1):23.
21.
Loo JA, Yan W, Ramachandran P, Wong DT. Comparative human salivary and plasma proteomes. J Dent Res. 2010;89(10):1016–23.
22.
Hyvärinen E, Savolainen M, Mikkonen JJW, Kullaa AM. Salivary metabolomics for diagnosis and monitoring diseases: challenges and possibilities. Metabolites. 2021;11(9):587.
23.
Ganguly U, Singh S, Pal S, Prasad S, Agrawal BK, Saini RV, et al. Alpha-synuclein as a biomarker of Parkinson’s disease: good, but not good enough. Front Aging Neurosci. 2021;13:702639.
24.
Yan SK, Wei BJ, Lin ZY, Yang Y, Zhou ZT, Zhang WD. A metabonomic approach to the diagnosis of oral squamous cell carcinoma, oral lichen planus and oral leukoplakia. Oral Oncol. 2008;44(5):477–83.
25.
Yang J, Xu R, Wang C, Qiu J, Ren B, You L. Early screening and diagnosis strategies of pancreatic cancer: a comprehensive review. Cancer Commun. 2021;41(12):1257–74.
26.
Hajishengallis E, Parsaei Y, Klein MI, Koo H. Advances in the microbial etiology and pathogenesis of early childhood caries. Mol Oral Microbiol. 2017;32(1):24–34.
27.
Belstrøm D. The salivary microbiota in health and disease. J Oral Microbiol. 2020;12(1):1723975.
28.
Heaney LM, Deighton K, Suzuki T. Non-targeted metabolomics in sport and exercise science. J Sports Sci. 2019;37(9):959–67.
29.
Liang CS, Ho PS, Shen LJ, Lee WK, Yang FW, Chiang KT. Comparison of the efficacy and impact on cognition of glycopyrrolate and biperiden for clozapine-induced sialorrhea in schizophrenic patients: a randomized, double-blind, crossover study. Schizophr Res. 2010;119(1–3):138–44.
30.
Zhu MH, Liu ZJ, Hu QY, Yang JY, Jin Y, Zhu N, et al. Amisulpride augmentation therapy improves cognitive performance and psychopathology in clozapine-resistant treatment-refractory schizophrenia: a 12-week randomized, double-blind, placebo-controlled trial. Mil Med Res. 2022;9(1):59.
31.
Fischer V, Vogels B, Maurer G, Tynes RE. The antipsychotic clozapine is metabolized by the polymorphic human microsomal and recombinant cytochrome P450 2D6. J Pharmacol Exp Ther. 1992;260(3):1355–60.
32.
Ishikawa S, Kobayashi M, Hashimoto N, Mikami H, Tanimura A, Narumi K, et al. Association between N-desmethylclozapine and clozapine-induced sialorrhea: involvement of increased nocturnal salivary secretion via muscarinic receptors by N-desmethylclozapine. J Pharmacol Exp Ther. 2020;375(2):376–84.
33.
Praharaj SK, Arora M, Gandotra S. Clozapine-induced sialorrhea: pathophysiology and management strategies. Psychopharmacology. 2006;185(3):265–73.
34.
Ekström J, Godoy T, Riva A. N-Desmethylclozapine exerts dual and opposite effects on salivary secretion in the rat. Eur J Oral Sci. 2010;118(1):1–8.
35.
Kır Y, Baskak B, Kuşman A, Sayar-Akaslan D, Özdemir F, Sedes-Baskak N, et al. The relationship between plasma levels of clozapine and N-desmethyclozapine as well as M1 receptor polymorphism with cognitive functioning and associated cortical activity in schizophrenia. Psychiatry Res Neuroimaging. 2020;303:111128.
36.
Ekström J, Godoy T, Loy F, Riva A. Parasympathetic vasoactive intestinal peptide (VIP): a likely contributor to clozapine-induced sialorrhoea. Oral Dis. 2014;20(3):e90–6.
37.
Duarte D, Castro B, Pereira JL, Marques JF, Costa AL, Gil AM. Evaluation of saliva stability for NMR metabolomics: collection and handling protocols. Metabolites. 2020;10(12):515.
38.
Candlish JK, Scougall RK. L-5-hydroxylysine as a constituent of the shell membranes of the hen’s egg. Int J Protein Res. 1969;1(4):299–302.
39.
Maffei ME. 5-Hydroxytryptophan (5-HTP): natural occurrence, analysis, biosynthesis, biotechnology, physiology and toxicology. Int J Mol Sci. 2020;22(1):181.
40.
Martin KS, Azzolini M, Lira Ruas J. The kynurenine connection: how exercise shifts muscle tryptophan metabolism and affects energy homeostasis, the immune system, and the brain. Am J Physiol Cell Physiol. 2020;318(5):C818–30.
41.
Kouno Y, Anraku M, Yamasaki K, Okayama Y, Iohara D, Nakamura H, et al. N-acetyl-L-methionine is a superior protectant of human serum albumin against post-translational oxidation as compared to N-acetyl-L-tryptophan. Biochem Biophys Rep. 2016;6:266–74.
42.
Zhang J, Wang N, Zhou Y, Wang K, Sun Y, Yan H, et al. Oridonin induces ferroptosis by inhibiting gamma-glutamyl cycle in TE1 cells. Phytother Res. 2021;35(1):494–503.
43.
Inoue M. Glutathionists in the battlefield of gamma-glutamyl cycle. Arch Biochem Biophys. 2016;595:61–3.
44.
Fuchs SA, Berger R, Klomp LW, de Koning TJ. D-amino acids in the central nervous system in health and disease. Mol Genet Metab. 2005;85(3):168–80.
45.
Cellitti SE, Ou W, Chiu HP, Grünewald J, Jones DH, Hao X, et al. D-Ornithine coopts pyrrolysine biosynthesis to make and insert pyrroline-carboxy-lysine. Nat Chem Biol. 2011;7(8):528–30.
46.
Pretorius CJ, Reade MC, Warnholtz C, McWhinney B, Phua MM, Lipman J, et al. Pyroglutamate (5-oxoproline) measured with Hydrophilic Interaction Chromatography (HILIC) tandem mass spectrometry in acutely ill patients. Clin Chim Acta. 2017;466:72–7.
47.
Kobuchi S, Akutagawa M, Ito Y, Sakaeda T. Association between the pharmacokinetics of capecitabine and the plasma dihydrouracil to uracil ratio in rat: a surrogate biomarker for dihydropyrimidine dehydrogenase activity. Biopharm Drug Dispos. 2019;40(1):44–8.
48.
Yu HM, Chiu CH, Chen WT, Wu CH, Lin PY, Huang YY, et al. Evaluation of 5-[(18)F] fluoro-2’-deoxycytidine as a tumor imaging agent: a comparison of [(18)F] FdUrd, [(18)F] FLT and [(18)F] FDG. Appl Radiat Isot. 2019;148:152–9.
49.
Vincenzetti S, Polzonetti V, Micozzi D, Pucciarelli S. Enzymology of pyrimidine metabolism and neurodegeneration. Curr Med Chem. 2016;23(14):1408–31.
50.
Le TT, Ziemba A, Urasaki Y, Hayes E, Brotman S, Pizzorno G. Disruption of uridine homeostasis links liver pyrimidine metabolism to lipid accumulation. J Lipid Res. 2013;54(4):1044–57.
51.
Zizzo MG, Mulè F, Mastropaolo M, Condorelli DF, Belluardo N, Serio R. Can guanine-based purines be considered modulators of intestinal motility in rodents? Eur J Pharmacol. 2011;650(1):350–5.
52.
Wang Y, Deng M, Deng B, Ye L, Fei X, Huang Z. Study on the diagnosis of gout with xanthine and hypoxanthine. J Clin Lab Anal. 2019;33(5):e22868.
53.
Galkin A. Brain ischemia/reperfusion injury and mitochondrial complex I damage. Biochemistry. 2019;84(11):1411–23.
54.
Hungerford JM. Histamine and scombrotoxins. Toxicon. 2021;201:115–26.
55.
Andersen G, Marcinek P, Sulzinger N, Schieberle P, Krautwurst D. Food sources and biomolecular targets of tyramine. Nutr Rev. 2019;77(2):107–15.
56.
Mittal R, Debs LH, Patel AP, Nguyen D, Patel K, O&apos;Connor G, et al. Neurotransmitters: the critical modulators regulating gut-brain Axis. J Cell Physiol. 2017;232(9):2359–72.
57.
He Q, Huang S, Wu Y, Zhang W, Wang F, Cao J, et al. Comparative study on the composition of free amino acids and derivatives in the two botanical origins of an edible Chinese herb “Xiebai,” i.e., Allium chinense G. Don and Allium macrostemon Bunge species. Food Res Int. 2018;106:446–57.
58.
Moore TC, Shaner CA. Synthesis of indoleacetic acid from tryptophan via indolepyruvic acid in cell-free extracts of pea seedlings. Arch Biochem Biophys. 1968;127(1):613–21.
59.
McGettrick AF, Corcoran SE, Barry PJ, McFarland J, Crès C, Curtis AM, et al. Trypanosoma brucei metabolite indolepyruvate decreases HIF-1α and glycolysis in macrophages as a mechanism of innate immune evasion. Proc Natl Acad Sci U S A. 2016;113(48):E7778–87.
60.
Lu PJ, Tucker JD, Branch EK, Guo F, Blaeser AR, Lu QL. Ribitol enhances matriglycan of α-dystroglycan in breast cancer cells without affecting cell growth. Sci Rep. 2020;10(1):4935.
61.
Cataldi MP, Lu P, Blaeser A, Lu QL. Ribitol restores functionally glycosylated α-dystroglycan and improves muscle function in dystrophic FKRP-mutant mice. Nat Commun. 2018;9(1):3448.
62.
Anunciato Casarini TP, Frank LA, Pohlmann AR, Guterres SS. Dermatological applications of the flavonoid phloretin. Eur J Pharmacol. 2020;889:173593.
63.
Stachulski AV, Berry NG, Lilian Low AC, Moores SL, Row E, Warhurst DC, et al. Identification of isoflavone derivatives as effective anticryptosporidial agents in vitro and in vivo. J Med Chem. 2006;49(4):1450–4.
64.
Mielcarek M, Isalan M. Kinetin stimulates differentiation of C2C12 myoblasts. PLoS One. 2021;16(10):e0258419.
65.
Asgharzade S, Khorrami MB, Forouzanfar F. Neuroprotective effect of herniarin following transient focal cerebral ischemia in rats. Metab Brain Dis. 2021;36(8):2505–10.
66.
Li N, Chen K, Dong H, Yang J, Yoshizawa M, Kagami H, et al. Alliin inhibits adipocyte differentiation by downregulating Akt expression: implications for metabolic disease. Exp Ther Med. 2021;21(6):563.
67.
Solismaa A, Kampman O, Seppälä N, Viikki M, Mäkelä KM, Mononen N, et al. Polymorphism in alpha 2A adrenergic receptor gene is associated with sialorrhea in schizophrenia patients on clozapine treatment. Hum Psychopharmacol. 2014;29(4):336–41.
68.
Rajagopal V, Sundaresan L, Rajkumar AP, Chittybabu C, Kuruvilla A, Srivastava A, et al. Genetic association between the DRD4 promoter polymorphism and clozapine-induced sialorrhea. Psychiatr Genet. 2014;24(6):273–6.
69.
Li Z, Liang D, Ye D, Chang HH, Ziegler TR, Jones DP, et al. Application of high-resolution metabolomics to identify biological pathways perturbed by traffic-related air pollution. Environ Res. 2021;193:110506.
70.
Ni H, Lu L, Deng J, Fan W, Li T, Yao J. Effects of glutamate and aspartate on serum antioxidative enzyme, sex hormones, and genital inflammation in boars challenged with hydrogen peroxide. Mediators Inflamm. 2016;2016:4394695.
71.
Fell MJ, Katner JS, Rasmussen K, Nikolayev A, Kuo MS, Nelson DL, et al. Typical and atypical antipsychotic drugs increase extracellular histamine levels in the rat medial prefrontal cortex: contribution of histamine h(1) receptor blockade. Front Psychiatry. 2012;3:49.
72.
Lévesque C, Hernandez G, Mahmoudi S, Calon F, Gasparini F, Gomez-Mancilla B, et al. Deficient striatal adaptation in aminergic and glutamatergic neurotransmission is associated with tardive dyskinesia in non-human primates exposed to antipsychotic drugs. Neuroscience. 2017;361:43–57.
73.
Su X, Li X, Wang H, Cai Z. Simultaneous determination of methionine cycle metabolites, urea cycle intermediates and polyamines in serum, urine and intestinal tissue by using UHPLC-MS/MS. Talanta. 2021;224:121868.
74.
Han G, Wei P, He M, Teng H, Chu Y. Metabolomic profiling of the aqueous humor in patients with wet age-related macular degeneration using UHPLC-MS/MS. J Proteome Res. 2020;19(6):2358–66.
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