Comparison of serum YKL-40 levels in schizophrenia patients with and without Type 2 Diabetes Mellitus and healthy controls

Introduction and Objective: Schizophrenia is a common chronic psychiatric disorder that causes significant morbidity and mortality. In recent years, interest in the role of inflammation and neuroinflammation in the etiopathogenesis of schizophrenia has increased. Similarly, inflammatory processes are known to play a fundamental role in the pathogenesis of Type 2 Diabetes Mellitus (T2DM). T2DM is observed more frequently in patients with schizophrenia compared to the general population. It is thought that some shared pathophysiological mechanisms, including inflammatory pathways, may contribute to the development of both schizophrenia and T2DM. In this study, we compared the serum levels of YKL-40, a pro-inflammatory biomarker, among schizophrenia patients without comorbid T2DM, schizophrenia patients with comorbid T2DM, and healthy controls. The aim of this study was to investigate whether there is a difference in serum YKL-40 levels among healthy controls, schizophrenia patients with comorbid T2DM, and those without T2DM, and to examine whether there is a relationship between serum YKL-40 levels and the severity of clinical symptoms in schizophrenia patients. This study aimed to investigate whether there is a difference in serum YKL-40 levels among healthy controls, schizophrenia patients with comorbid type 2 diabetes mellitus (T2DM), and those without T2DM and to examine whether there is a relationship between serum YKL-40 levels and the severity of clinical symptoms in schizophrenia patients. Materials and Methods: A total of 108 participants were included in the study: 36 schizophrenia patients without comorbid T2DM, 36 schizophrenia patients with comorbid T2DM, and 36 healthy controls. Participants were matched for age, sex, and years of education. After obtaining informed consent from all participants, sociodemographic and clinical data forms were completed, and patients were evaluated using the Structured Clinical Interview for DSM-IV (SCID-I). The Positive and Negative Syndrome Scale (PANSS) and Clinical Global Impression – Severity subscale (CGI-S) were administered to the patient groups. Serum samples were collected from both patients and controls to measure YKL-40 levels. Venous blood samples were collected from all participants, and serum YKL-40 levels were measured in the laboratory using an ELISA kit. SPSS 27.0 statistical package program was used in the analysis of the data. Results and Conclusion: Our study found no statistically significant differences in serum YKL-40 levels among schizophrenia patients without T2DM, those with T2DM, and the healthy control group. Our study results suggest that YKL-40 may not be a reliable biomarker for differentiating between these groups. We also found no correlations between YKL-40 levels and disease severity indicators such as PANSS and CGI-S scores in either schizophrenia group, indicating that YKL-40 may not be a valuable marker for disease severity. Additionally, there was no significant association between YKL-40 levels and age at onset, duration of illness, or number of hospitalizations. Although previous studies have examined serum YKL-40 levels in schizophrenia and T2DM separately, to our knowledge, this is the first study to compare YKL-40 levels in schizophrenia patients with comorbid T2DM, schizophrenia patients without T2DM, and healthy controls. Thus, our study is among the first to evaluate the relationship between YKL-40 and both schizophrenia and metabolic disorders within the same sample. These findings suggest that further studies with larger sample sizes, including drug-naive first-episode psychosis patients and longitudinal designs, are needed to better understand the relationship between YKL-40 levels and comorbid metabolic conditions in schizophrenia.