Association between IL-6 and metabolic syndrome in schizophrenia patients treated with second-generation antipsychotics

OBJECTIVE: Second-generation antipsychotics (SGAs) have a high risk of causing metabolic syndrome (MetS). There is accumulating evidence supporting the fact that the activation of inflammatory pathway contributes to the development of MetS and further aggravates cognitive impairment. This study aimed to investigate the relationship between interleukin-6 (IL-6), cognitive function, and MetS in schizophrenia patients treated with SGAs. METHODS: One hundred and seventy-four patients with schizophrenia using SGAs were divided into MetS and non-MetS group, based on the criteria of the National Cholesterol Education Program’s Adult Treatment Panel III. Cognitive function was measured using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). A total of 138 patients and 29 healthy controls were examined in the plasma IL-6 levels. RESULTS: The prevalence of MetS in schizophrenia patients treated with SGAs was 33% in this study. There were no significant differences in cognitive functions (both RBANS total score and subscale score) between MetS and non-Mets patients (P>0.05). Patients with MetS had higher plasma levels of IL-6 compared to non-MetS patients (P=0.019). However, such difference was only found in male patients (male: P=0.012; female: P=0.513). The partial correlational analysis further showed that IL-6 levels were notably negative related to the HDL levels in male schizophrenia patients after age, years of education, body mass index (BMI), age of onset, total disease course, and equal dose of olanzapine were controlled (male: P=0.009; female: P=0.450). In addition, the multiple regression analysis (stepwise model) performed in the male patient subgroup showed that IL-6 (beta =−0.283, t=−2.492, P=0.015) was an independent contributor to the HDL levels. However, the IL-6 was not an independent contributor to the HDL levels in female patients. CONCLUSION: Our findings provide evidence suggesting that the immune-inflammatory effect of IL-6 on SGAs-induced MetS may be in a gender manner.