Changes in plasma glycine, l-serine, and d-serine levels in patients with schizophrenia as their clinical symptoms improve: Results from the Juntendo University Schizophrenia Projects (JUSP)

Biomarkers in schizophrenia: A focus on blood based diagnostics and theranostics

“…A single study has reported that people with Sz had higher levels of plasma agmatine, an endogenous substance that is synthesized from Larginine and is proposed to be a new neurotransmitter, than controls [88] , and that the levels correlated with their PANSS score, suggesting that plasma agmatine levels may be a potential diagnostic biomarker for Sz. Lower plasma D-serine, D-/L-serine ratio were found in people with Sz who were treatmentresistant [89] , but chronically people with Sz showed higher plasma D-serine and glycine levels [92] . In addition, the plasma levels of D-serine were associated with improvements in positive symptom [92] , but not with cognitive functions in people with Sz [93] .…”

“…Lower plasma D-serine, D-/L-serine ratio were found in people with Sz who were treatmentresistant [89] , but chronically people with Sz showed higher plasma D-serine and glycine levels [92] . In addition, the plasma levels of D-serine were associated with improvements in positive symptom [92] , but not with cognitive functions in people with Sz [93] . A study examining the effects of clozapine treatment on D-serine, L-serine, and glycine in people with Sz who were treatmentresistant, showed glycine levels and the glycine/Lserine ratio were significantly increased following clozapine treatment, suggesting that plasma Lserine and glycine could be potential therapeutic markers [89] .…”

Meta-Analysis of the Efficacy of Adjunctive NMDA Receptor Modulators in Chronic Schizophrenia

“…[29] Reduction of D-serine and elevation of L-serine CSF levels have been found in drugnaive patients with schizophrenia, [30,31] indicating dysfunction of SR activity in schizophrenia. [32] Improvement in symptoms of schizophrenia positively correlates with elevation in D-serine levels, [33] and the severity of negative symptoms inversely correlates with circulating levels of glycine, [34,35] which rise with amelioration of negative symptoms. [36] In addition, there are reports of associations between schizophrenia and gene G72, and between G72 and DAAO, [37] the enzyme that is involved in the metabolism of D-serine.…”

Analysis of free d-serine in mammals and its biological relevance

“…Further evaluation, however, is needed to clarify the significance of these results because (a) the results of the quantitative analysis of d-serine in the blood and cerebrospinal fluid of schizophrenic patients are controversial [142][143][144] and (b) the effects of a variety of factors that may influence the blood d-serine concentrations such as the medication, d-serine-containing foods and diurnal variation of d-serine metabolism cannot be excluded in these studies.…”