Brain-Derived Neurotrophic Factor (BDNF) and Serotonin Transporter (SERT) in Platelets of Patients with Mild Huntington’s Disease: Relationships with Social Cognition Symptoms

Deficits in social-cognition processing have been identified during early stages of Huntington Disease (HD), attracting interest on their relevance as possible predictors of  neurodegenerative progression. Since the neurotrophin Brain-Derived Neurotrophic Factor (BDNF) and the serotonin (5-HT) transporter (SERT) are known to modulate human adaptive behavior, we appraised these two proteins in mild-HD using blood platelets, with the aim at finding relationships with cognitive/psychosocial skills. Thirteen gene positive and symptomatic patients (9M/4W, HD-stage II, age> 40y) together 11 gender/age matched controls without a concurrent diagnosis of psychiatric disorders, underwent a blood test to determine BDNF storage and membrane-bound SERT in platelets by an ELISA immune-enzyme dosage and [ 3 H]-paroxetine ([ 3 H]-PAR) binding, respectively. Enrolled subjects were concurrently evaluated through a battery of socio-cognitive tests and emotion recognition questionnaires. Results showed greater intra-platelet BDNF (~ +20-22%) in patients versus controls, whereas equilibrium [ 3 H]-PAR binding parameters, maximum density (B max ) and dissociation constant (K D ), did not appreciably vary in the two comparison groups. Cognitive/emotion abilities were found significantly reduced in patients. Additionally, platelet BDNF was unrelated to psycho-cognitive scores, but positively correlated with the illness duration. As well, SERT B max was unconnected to HD signs or socio-cognitive scores, whilst K D s negatively correlated with scores for angry voice recognition in both controls and patients. This pilot study suggests that platelet BDNF and SERT do not specifically underlie psychosocial deficits in stage II-HD, while higher BDNF storage in delayed mild symptoms, would derive from compensatory mechanisms. Supplementary investigations are warranted, by also comparing patients in other illness’s phases.