title: Reduced plasma serotonin and 5-hydroxyindoleacetic acid levels in Parkinson's disease are associated with nonmotor symptoms.
abstract: BACKGROUND
  Accumulating evidence suggests that serotonergic system may be implicated in the pathophysiology of Parkinson's disease (PD), and particularly in nonmotor symptoms such as depression, fatigue, sleep disorders, sensory and autonomic dysfunction. This study aimed to evaluate plasma levels of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in PD patients, and investigate their associations with nonmotor symptoms.
  
  
  METHODS
  Eighty-two PD patients and sixty-four controls underwent a series of clinical assessments, including Hamilton Depression Scale, Fatigue Severity Scale, Pittsburgh Sleep Quality Index, Visual Analog Scale for Pain, and Scale for Outcomes in PD for Autonomic Symptoms. Plasma 5-HT and 5-HIAA levels were measured by HPLC-ECD.
  
  
  RESULTS
  PD patients exhibited worse performance on nonmotor symptom scales (all P-values <0.001) and presented lower plasma levels of 5-HT (P < 0.001) and 5-HIAA (P < 0.001) than control individuals. Within the PD group, decreased concentrations of plasma 5-HT and 5-HIAA were correlated with more severe depression (r = -0.447, P < 0.001; r = -0.407, P < 0.001, respectively) and pain (r = -0.485, P < 0.001; r = -0.416, P < 0.001, respectively). After performing multiple linear regression, plasma 5-HT (P = 0.01) and 5-HIAA (P = 0.006) remained significantly associated with depression.
  
  
  CONCLUSIONS
  Our results suggest that serotonergic dysfunction might exist in PD, and specifically correlated with depression and pain in PD. Plasma levels of 5-HT and 5-HIAA may be considered as peripheral markers for depression in PD.
authors.affiliation: Department of Neurology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Tong
authors.affiliation: Department of Neurology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Neurology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: Department of Neurology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.
authors.forename: Siming
authors.initials: S
authors.lastname: Jiang
authors.affiliation: Department of Neurosurgery, Nanjing Children's Hospital of Nanjing Medical University, Nanjing 210029, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Neurology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.
authors.forename: Qinrong
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Department of Neurology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Ding
authors.affiliation: Department of Laboratory Medicine, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China.
authors.forename: Daqian
authors.initials: D
authors.lastname: Li
authors.affiliation: Department of Microbiology and Immunology, Nanjing Medical University, Nanjing 210029, China.
authors.forename: Xiaobin
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Neurology, The First Affiliated Hospital of Nanjing Medical University, Nanjing 210029, China. Electronic address: kezhong_zhang1969@126.com.
authors.forename: Kezhong
authors.initials: K
authors.lastname: Zhang
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D003863:Depression / Q000097:blood* / Q000209:etiology; D005260:Female; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000097:blood*; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000097:blood* / Q000209:etiology; D010300:Parkinson Disease / Q000097:blood* / Q000150:complications / Q000503:physiopathology*; D012701:Serotonin / Q000097:blood*; D012720:Severity of Illness Index
chemical_list: D015415:Biomarkers; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid
keywords: 5-Hydroxyindoleacetic acid; Depression; Pain; Parkinson's disease; Serotonin