title: Opiorphin in burning mouth syndrome patients: a case-control study.
abstract: OBJECTIVE
  Opiorphin is a pentapeptide isolated from human saliva that suppresses pain from chemically induced inflammation and acute physical pain. Burning mouth syndrome (BMS) is a chronic condition of a burning sensation in the mouth, where no underlying dental or medical cause can be identified. We aimed to measure the level of opiorphin in whole unstimulated (UWS) and stimulated (SWS) saliva of patients with BMS.
  
  
  METHODS
  Originally developed and validated LC-MS/MS method was used for opiorphin quantification. Samples were obtained from 29 BMS patients and 29 age- and sex-matched controls.
  
  
  RESULTS
  The average concentration of opiorphin in UWS and SWS in the BMS group was 8.13 ± 6.45 and 5.82 ± 3.59 ng/ml, respectively. Opiorphin in BMS patients' UWS was significantly higher, compared to the control group (t = 2.5898; p = 0.0122). SWS opiorphin levels were higher, but not significantly, in BMS patients than in controls.
  
  
  CONCLUSIONS
  Our results indicate that higher quantities of salivary opiorphin in BMS may be a consequence of chronic pain, but we cannot exclude that they occur as a result of emotional and behavioral imbalances possibly associated with BMS. To our knowledge, this is the first original article measuring opiorphin in a pain disorder.
  
  
  CONCLUSIONS
  Opiorphin may be a measurable biomarker for chronic pain, which could help in objectifying otherwise exclusively a subjective experience. Increased opiorphin could serve as a universal objective indicator of painful conditions. Since opiorphin may also reflect emotional and socio-relational imbalances occurring with BMS, it could as well represent a biomarker for BMS. Knowledge on opiorphin's involvement in pain pathways could contribute to developing new clinical diagnostic methods for BMS.
authors.affiliation: Department of Oral and Maxillofacial Surgery, University of Zagreb School of Dental Medicine University Hospital Dubrava, Av. Gojka Šuška 6, 10000, Zagreb, Croatia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Salarić
authors.affiliation: Department of Craniofacial Development and Stem Cell Biology, Guy's Hospital, King's College London, Great Maze Pond, London, SE1 9RT, UK.
authors.forename: Maja
authors.initials: M
authors.lastname: Sabalić
authors.affiliation: Department of Oral Medicine, University of Zagreb School of Dental Medicine and University Hospital Centre Zagreb, Gundulićeva 5, 10000, Zagreb, Croatia. alajbeg@sfzg.hr.
authors.forename: Ivan
authors.initials: I
authors.lastname: Alajbeg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002054:Burning Mouth Syndrome / Q000378:metabolism*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009842:Oligopeptides / Q000378:metabolism*; D012463:Saliva / Q000737:chemistry*; D012471:Salivary Proteins and Peptides / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D009842:Oligopeptides; D012471:Salivary Proteins and Peptides; C517879:glutaminyl-arginyl-phenylalanyl-seryl-arginine
keywords: Burning mouth syndrome; Chromatography, Liquid; Opiorphin; Saliva; Spectrometry, Mass