The relationship between pain symptom severity, salivary opiorphin levels and target microrna expression in depressive disorder patients

AIM: The aim of our research is to determine the relationship between salivary opiorphin levels, miRNA-138-5p levels, and pain severity in healthy volunteers and patients diagnosed with major depressive disorder with chronic pain complaints, and to reveal the regulation of miRNA-138-5p on salivary opiorphin levels. Our hypothesis is that patients diagnosed with major depressive disorder with chronic pain complaints will have higher miR-138-5p expression levels, lower salivary opiorphin levels, and that there will be a correlation between salivary opiorphin levels, miR-138-5p levels, and the severity of depression and pain symptoms. METHODS: The study included 48 patients diagnosed with major depressive disorder according to DSM-V criteria and assessed with SCID-5-CV, who presented to the Psychiatry Outpatient Clinic of Balıkesir University Health Practice and Research Hospital, as well as 48 healthy volunteers. After obtaining written consent from the patients, face-to-face interviews were conducted using the Sociodemographic Data Form, Hamilton Depression Rating Scale (HAM-D), Brief Pain Inventory-Short Form (BPI-SF), and Visual Analog Scale (VAS) tests. Measurements of miR-138-5p levels in blood and opiorphin levels in saliva were performed in genetic and biochemistry laboratories using RT-PCR and ELISA methods. RESULTS: In our study, when comparing the miR-138-5p levels of the participants included in the research, it was found that the miR-138-5p levels of the case group were higher than those of the control group (z: -2.71; p: 0.007). When comparing miR-138-5p levels according to HAM-D depression severity, it was determined that individuals with mild and moderate depression had higher miR-138-5p levels than those without depression (KW: 8.73; p: 0.01). When comparing miR-138-5p levels according to VAS pain severity, it was found that individuals with pain symptoms had higher miR-138-5p levels than those without pain symptoms (KW: 10.39; p: 0.02). When comparing salivary opiorphin levels among the groups, no statistically significant difference was found between the case and control groups (t: 0.14; p: 0.88). When comparing the salivary opiorphin levels of the case group according to VAS scores in terms of pain severity, no statistically significant difference was found (F: 1.20; p: 0.36). When comparing the salivary opiorphin levels of the case group according to HAM-D depression severity, no statistically significant difference was found (F: 0.42; p: 0.66). No statistically significant correlation was found between miR-138-5p levels and salivary opiorphin levels among the participants (r: 0.11; p: 0.43). CONCLUSION: Considering the results of our study, it has been demonstrated that changes in miRNA-138-5p levels are effective in the pain mechanism and play a significant role in the etiology and symptomatology of major depressive disorder (MDD), consistent with our hypothesis. No significant relationship was found between salivary opiorphin levels and the severity of depression and pain. Our research highlights that miRNA-138-5p could be used as a diagnostic tool and a therapeutic intervention target in terms of depression severity and pain severity in MDD patients, and it paves the way for future studies.