Purpose: Depressive mood is a major psychiatric symptom that causes serious disturbances in daily life. Unlike physical symptoms, psychiatric symptoms are more difficult to evaluate objectively. Therefore, we aimed to discover biomarkers that reflect changes in serum protein metabolism during a clinical depressive mood. Methods: Serum protein profiling was conducted in participants who were not experiencing a current depressive episode (healthy individuals and patients in remission). Serum proteins were identified and quantified using liquid chromatography–tandem mass spectrometry. Differentially expressed proteins with a p-value < 0.05 were selected, and candidate biomarkers were verified using multiple reaction monitoring analysis for absolute quantification. Results: Apolipoprotein A-IV levels were lower in the group with a current episode of depression than in the remission and healthy control groups. Further, fibronectin levels were also lower in the group with a current episode of depression than in the healthy control group but not in the remission group. Conclusion: We found that apolipoprotein A-IV-mediated inflammation is involved in clinical depressive moods, possibly by inducing neurological changes in the brain. Therefore, apolipoprotein A-IV and fibronectin levels may be explored as potentially novel biomarkers for detecting a current episode of depression.

Ergothioneine, which is a naturally occurring metabolite, generally accumulates in tissues and cells subjected to oxidative stress, owing to its structural stability at physiological pH; therefore, it has been attracting attention in various biomedical fields. Ergothioneine has also been suggested as a potential forensic marker, but its applicability has not yet been quantitatively validated. In this study, quantitative analysis of ergothioneine in bloodstains was conducted to estimate the age of bloodstains and that of bloodstain donors. Blood from youth and elderly participants was used to generate bloodstains. After extracting metabolites from the bloodstains under prevalent age conditions, ergothioneine levels were quantified by mass spectrometry via multiple reaction monitoring. The concentration of ergothioneine in day 0 bloodstains (fresh blood), was significantly higher in the elderly group than in the youth group, but it did not differ by sex. Statistically significant differences were observed between the samples from the two age groups on days 0, 5 and 7, and on days 2 and 3 compared with day 0. The findings suggest that ergothioneine can be used to estimate the age of bloodstains and of the donor; it could be useful as a potential marker in reconstructing crime scenes.

Seungyeon LEE, Jiyeong LEE. Korean J Clin Lab Sci. 2025;57:181-8. https://doi.org/10.15324/kjcls.2025.57.2.181

Objective: Spontaneous remission may influence the outcome of clinical trials and evaluation of antidepressant efficacy, as it is associated with placebo effects and false remission rates. However, the characteristics of spontaneous remission and its biological mechanisms remain poorly understood. This study aimed to explore the metabolic signatures and underlying biological mechanisms of spontaneous remission using metabolomics. Methods: This study conducted untargeted and targeted metabolomic analyses in a discovery cohort (n = 16) comprising patients with major depressive disorder (MDD) and those who were spontaneously remitted without medication. Findings were validated in an independent cohort (n = 185), comprising drug-treated patients and healthy controls. Results: Acetylcarnitine levels were significantly increased in spontaneous remission compared to depression, whereas glycerophosphocholine levels were decreased in spontaneous remission. Both metabolites showed the highest concentration in the control group, followed by the remission group, and the lowest concentration in the depression group, regardless of medication status. These changes suggest alterations in mitochondrial and membrane lipid metabolism. Conclusion: Altered levels in acetylcarnitine and glycerophosphocholine may reflect key pathogenic mechanisms of MDD. These findings offer new insight into spontaneous remission as a distinct clinical subtype of depression and may highlight the potential of these metabolites as biomarkers for treatment monitoring in MDD.Keywords: Depressive disorder, major; Remission, spontaneous; Metabolomics; Acetylcarnitine; Glycerophosphocholine

Seungyeon LEE, Hee-Gyoo KANG. Korean J Clin Lab Sci. 2025;57:320-8. https://doi.org/10.15324/kjcls.2025.57.3.320