Gender differences in dopaminergic system dysfunction in de novo Parkinson's disease clinical subtypes

Parkinson's disease (PD) is characterized by heterogeneity in clinical syndromes, prognosis, and pathophysiology mechanisms. Gender differences in neural anatomy and function are emerging as fundamental determinants of phenotypic variability. Different clinical subtypes, defined as mild motor predominant, intermediate, and diffuse-malignant, have been recently proposed in PD. This study investigated gender influence on clinical features, dopaminergic dysfunction, and connectivity in patients with de novo idiopathic PD stratified according to the clinical criteria for subtypes (i.e., mild motor, intermediate, and diffuse-malignant). We included 286 drug-naïve patients (Males/Females: 189/97, age [mean ± standard deviation]: 61.99 ± 9.67; disease duration: 2.08 ± 2.21) with available [123I]FP-CIT-SPECT and high-resolution T1-weighted MRI from the Parkinson's Progression Markers Initiative. We assessed gender differences for clinical and cognitive features, and dopaminergic presynaptic dysfunction in striatal or extra-striatal regions using molecular analysis of [123I]FP-CIT-bindings. We applied an advanced multivariate analytical approach - partial correlations molecular connectivity analyses - to assess potential gender differences in the vulnerability of the nigrostriatal and mesolimbic dopaminergic pathways. In the mild motor and intermediate subtypes, male patients with idiopathic PD showed poorer cognitive performances than females, who - in contrast - presented more severe anxiety symptoms. The male vulnerability emerged also in the motor system in the same subtypes with motor impairment associated with a lower dopamine binding in the putamen and more severe widespread connectivity alterations in the nigrostriatal dopaminergic pathway in males than in females. In the diffuse-malignant subtype, males showed more severe motor impairments, consistent with a lower dopamine uptake in the putamen than females. On the other hand, a severe dopaminergic depletion in several dopaminergic targets of the mesolimbic pathway, together with extensive altered connectivity in the same system, characterized females with idiopathic PD in all the subtypes. The anxiety level was associated with a lower dopaminergic binding in the amygdala only in females. This study provides evidence on gender differences in idiopathic PD across clinical subtypes, and, remarkably, since the early phase. The clinical correlations with the nigrostriatal or mesolimbic systems in males and females support different vulnerabilities and related disease expressions. Gender differences must be considered in a precision medicine approach to preventing, diagnosing, and treating idiopathic PD.