CCL11 levels in drug-naive bipolar patients: The role of sex and smoking status

Background It has been reported that patients with bipolar disorder (BD) present changes in peripheral levels of the inflammatory cytokine CCL11, particularly at latestages. The aim of this study is to evaluate CCL11 levels in a population-based sample of drug-naive young adults. Methods This is a cross-sectional study nested to a large population-based study. 29 drug-naive young adults with BD and 29 controls selected from this cohort were matched for sex, age, and years of education. The diagnosis of psychiatric disorders was performed using the Mini International Neuropsychiatric Interview PLUS. Serum levels of CCL11 were measured using sandwich-ELISA. Independent samples T-test was used to assess differences between groups regarding CCL11 levels. Multivariate linear regression analyses were used to evaluate the effect of independent factors on CCL11 levels. Results There were no demographic differences between individuals with BD and controls. No significant differences were found regarding CCL11 levels between groups. The final multivariate model showed that the variables that remained independently associated with higher CCL11 levels were male sex (B:41.41 [CI95%: 15.66 - 67.15], p = 0.002) and tobacco use (B:22.71 [CI95%: 1.28 - 44.15], p = 0.038). Conclusions The present study suggests that there is a possible influence of sex and tobacco use on CCL11 levels, as male sex and smoking status were associated with higher CCL11 levels in our sample. It also suggests that peripheral levels of CCL11 may not be involved in the pathophysiology of BD at early stages of the disorder.