Evolution of BDNF Full-Length/Truncated Receptor Ratio and Cognitive/General Functioning After a First Episode of Psychosis

Abstract

Brain plasticity has demonstrated to play a role in the pathophysiology of schizophrenia. Cognitive deterioration in these patients can be prevented by ensuring the adequate functioning of signaling pathways associated with brain plasticity. As BDNF exerts its action through receptors, in this study, we hypothesized that levels of some BDNF receptors during a first episode of psychosis (FEP) would correlate with the cognitive and global functioning of patients in the long term. We also hypothesized that the improvement of the ratio of full-length (TrKB-FL) and truncated (TrKB-T) TrKB receptors, and the predominance of the full-length isoform would be associated with better cognition and functioning. Peripheral levels of full-length (TrKB-FL) and truncated (TrKB-T) TrKB receptors were assessed in a sample of 97 FEP patients and 97 matched healthy controls. TrKB-FL/TrKB-T ratio(hereinafter, FL/T) was calculated for each patient. Cognitive and global functioning was measured at inclusion and at two years. A high baseline FL/T ratio was found to be related to a better cognitive function (global cognition, verbal memory, working memory and premorbid IQ). Cognitive performance at disease onset and at two years improved when the levels of the ratio were higher than one, with functional BDNF receptor (TrKB-FL) exceeding the value of the truncated isoform (TrKB-T). In addition the increase in the FL/T ratio during the two years of follow-up had positive effects on global functioning. This may be due either to a reduction in TrKB-T or to an increase in TrKB-FL, or both. In conclusion FL / T ratio was related to general functioning and cognition in the long-term.