[Schizophrenia, genetics and cognition]

Enzymatic activity of palmitoyl-protein thioesterase-1 in serum from schizophrenia significantly associates with schizophrenia diagnosis scales

Genome-wide association studies have confirmed that schizophrenia is an inheritable multiple-gene mental disorder. Longitudinal studies about depression, first episode psychosis (FEP) and acute psychotic relapse have mostly searched for brain imaging biomarkers and inflammatory markers from the blood. However, to the best of our knowledge, the association between enzymatic activities with diagnosis or prediction of treatment response in people with schizophrenia has barely been validated. Under the Longitudinal Study of National Mental Health Work Plan (2015-2020), we have studied a subsample of approximately 36 individuals from the cohort with data on palmitoyl-protein thioesterase-1 enzymatic activity from FEP and performed a bivariate correlation analysis with psychiatric assessment scores. After adjusting for sex, age, body mass index (BMI) and total serum protein, our data demonstrated that PPT1 enzymatic activity is significantly associated with schizophrenia and its Positive and Negative Syndrome Scale (PANSS) scores. This longitudinal study compared the PPT1 enzymatic activity in FEP schizophrenia patients and healthy volunteers, and the former exhibited a significant 1.5-fold increase in PPT1 enzymatic levels (1.79 mmol/L/h/mL, and 1.18 mmol/L/h/mL; P < 0.05; 95% CI, 2.3-2.9 and 1.4-1.8). The higher PPT1 enzymatic levels in FEP schizophrenia patients were positively associated with larger PANSS scaling scores (r = 0.32, P = 0.0079 for positive scaling; r = 0.41, P = 0.0006 for negative scaling; r = 0.45, P = 0.0001 for general scaling; and r = 0.34, P = 0.0048 for PNASS-S scaling). Higher enzymatic PPT1 in FEP schizophrenia patients is significantly associated with increased PANSS scaling values, indicating more serious rates of developing psychosis. Enzymatic activity of PPT1 may provide an important new view for schizophrenia disorders.

[Endophenotypes: the molecular biology point of view]

Endophenotypes are proposed for a better understanding of the molecular substrate underlying psychiatric disorders vulnerability. In this review, we discuss key points of the definition of endophenotypes from the molecular biology point of view. First, we examine the concept of heritability of endophenotype, which does not directly explain the molecular mechanisms responsible for the studied disorder Indeed, we discuss the necessity to better decipher the functional role of polymorphisms associated to endophenotypes, especially if those endophenotypes would be assigned a clinical and biological value. The complexity of endophenotypes definition and use in psychiatric research is also illustrated by the complexity of the human genome organization and gene networks as well as by the gene x environment interactions and also the possible existence of phenocopies.