Negative Symptoms of Schizophrenia Are Linked With Olfaction Deficits

Abstract

This study proposed a link between schizophrenia symptoms and expression of chondrotin sulfate proteoglycans (CSPGs), a modified protein widely found in the olfactory epithelium. The study compares symptoms between bipolar disorder and schizophrenia to CSPG cellular protein expression, or biological measurements that represent cellular protein levels. While existing literature exists on the relationship between CSPG cellular protein expression and psychotic disorders, a strong body of work translating biologic markers to psychiatric diagnosis was lacking. The central hypotheses of the study is a correlation between CSPG expression in the olfactory system that may be altered in individuals with psychotic disorders and correlated to specific symptoms. Also examined in this study was the correlation between negative symptoms and CSPG expression. Participants in the study were patients who were diagnosed with Schizophrenia and Bipolar disorder, recruited through clinicians and flyers, at McLean Hospital. Control samples were recruited through Massachusetts Eye and Ear Institute. Experienced clinicians administered both a psychiatric battery and olfactory epithelial biopsy. The psychiatric battery consisted of the Structured Clinical interview for DSM IV (SCID), both for control and psychiatric subjects, the Positive and Negative Syndrome Scale (PANSS) for only psychiatric subjects, and the Physical and Social Anhedonia Scale, also for only psychiatric subjects. The psychometrics were administered by a board certified psychiatrist and then graded by the thesis author for subsequent data analysis for this report. The biopsies were performed on subjects either on the hospital unit at McLean, or during nasal surgery at Massachusetts Eye and Ear Infirmary. These biopsies were then cultured for western blot analysis and measured for protein expression. The results showed correlations between CS6, or CSPG protein expression, and psychiatric samples. Specifically, the negative symptom, “diminished thinking,” was correlated to reduced CSPG expression in schizophrenia, as well as, correlated to reduced CSPG expression in psychiatric subjects, when compared to controls. Furthering the negative symptom narrative, CSPG expression was close to correlation with a negative symptom scale of the PANSS, Negative PANSS, only in subjects with schizophrenia, and was significant when an outlier was removed. This study provides additional supporting evidence in the relationship between CSPG deficits and negative symptoms in schizophrenia.