Plasma β-Endorphin Concentration and Antipsychotic Treatment Outcome in Schizophrenia: 1-Year Follow-Up

Plasma neuropeptide levels in patients with schizophrenia, bipolar disorder, or major depressive disorder and healthy controls: A multiplex immunoassay study

“…The present study revealed that there was no significant difference in plasma α-MSH, β-endorphin, neurotensin, oxytocin, and substance P levels between 149 patients with schizophrenia, 115 patients with BD, and 186 patients with MDD and 350 healthy controls. Our findings on β-endorphin and oxytocin are inconsistent with previous studies reporting higher plasma β-endorphin levels in patients with schizophrenia (patient: n = 43, 77, and 49 vs control: n = 34, 74, 47), [29][30][31] lower plasma oxytocin levels in patients with schizophrenia (patient: n = 34, 34, and 30 vs control: n = 31, 31, and 21), [33][34][35] higher and lower plasma oxytocin levels in patients with BD II (patient: n = 135 and 25 vs control: n = 119 and 29), 36,37 and lower plasma oxytocin levels in patients with MDD (patient: n = 61 vs control: n = 60). 38 In addition, a preclinical study reported increased neurotensin and oxytocin in genetic and/or environmental schizophrenia-like mice using multiplex immunoassay.…”

“…38 In addition, a preclinical study reported increased neurotensin and oxytocin in genetic and/or environmental schizophrenia-like mice using multiplex immunoassay. 41 Our finding is based on more patients than those of most previous studies [29][30][31][33][34][35]37,38,40 and rather support unaltered plasma oxytocin levels in schizophrenia, BD, or MDD in a systematic review and meta-analysis 32 or plasma substance P levels in patients with schizophrenia (patient: n = 43 vs control: n = 34) 31 and patients with MDD (patient: n = 42 vs control: n = 57). 40 Furthermore, to the best of our knowledge, this study is the first to show that plasma α-MSH and neurotensin levels are not altered in patients with schizophrenia, BD, or MDD.…”

“…Although the association between β-endorphin and MDD pathophysiology has been suggested, 16,17 such association was tested only in patients with schizophrenia showing that plasma β-endorphin levels were higher in 43, 77, and 49 patients with schizophrenia than in 34, 74, and 47 healthy controls, respectively. [29][30][31] A systematic review and meta-analysis reported that cerebrospinal fluid (CSF) and plasma oxytocin levels were not altered in patients with schizophrenia, BD, or MDD compared with those in healthy controls, 32 whereas the association of oxytocin with social anxiety or socio-emotional behavior has been suggested in patients with schizophrenia and MDD. 25,26 However, plasma oxytocin levels were lower in 34 patients with schizophrenia than in 31 healthy controls, 33 which was associated with poorer metacognition, but not with social cognition or neurocognition.…”

Alterations of serum neuropeptide levels and their relationship to cognitive impairment and psychopathology in male patients with chronic schizophrenia

“…However, these five neuropeptides have only recently been studied and previous results did not reveal significant differences between schizophrenic patients and HC 54 . Interestingly, there have also been studies showing significantly higher levels of BE in schizophrenic patients 55 , 56 , and others have concluded that low levels of OT are associated with SCZ 57 , 58 . Surprisingly, other studies have found that OT levels are high in patients with SCZ 59 – 61 .…”