title: Increased Dipeptidyl Peptidase-4 Activity Is Associated With High Prevalence of Depression in Middle-Aged and Older Adults: A Cross-Sectional Study.
abstract: OBJECTIVE
  Obesity, inflammation, and decreased neuropeptide Y (NPY) are risk factors for depression. Dipeptidyl peptidase-4 (DPP4), a newly identified adipokine, has been proved to promote inflammation and NPY degradation. Hence, we aimed to investigate the association between plasma DPP4 activity and depression symptoms in middle-aged and older adults.
  
  
  METHODS
  We cross-sectionally assessed 1,335 Chinese adults aged 45-76 years recruited from the Medical Examination Center, Guilin, China, between 2013 and 2014. The main outcome measures were plasma DPP4 activity, inflammatory markers, and NPY. Depression symptoms were determined by the score on the 9-item Patient Health Questionnaire (PHQ-9). Each of the 9 depression items of the PHQ-9 correspond to 1 of the DSM-IV diagnostic criteria for symptoms of major depressive disorder.
  
  
  RESULTS
  Subjects in the highest quartile of DPP4 activity had higher body mass index (BMI), interleukin-6 (IL-6), high-sensitivity C-reactive protein (hs-CRP), and PHQ-9 score compared with subjects in the lowest quartile (P < .05). Compared to patients without depression symptoms, patients with depression symptoms had higher BMI, waist-to-hip ratio, IL-6, hs-CRP, and DPP4 activity (P < .05). DPP4 activity was associated positively with IL-6, hs-CRP, and PHQ-9 score and negatively with NPY after adjustment for potential confounders (P < .05). The risk for depression symptoms increased with higher levels of DPP4 activity and inflammation and lower levels of NPY.
  
  
  CONCLUSIONS
  Increased DPP4 activity is independently associated with depression symptoms in middle-aged and older adults. The mechanisms might be partly explained by mutual influence among inflammation, NPY, and DPP4. These observations raise further interest in DPP4 activity for the potential effect on inflammation and NPY metabolism, as a risk biomarker, or even a possible therapeutic target for depression.
  
  
  BACKGROUND
  Chinese Clinical Trial Registry (ChiCTR-EPC-14005273).
authors.affiliation: Department of Endocrinology and Metabolism, The Second Affiliated Hospital of Guilin Medical University, 212, Renmin Rd, Guilin, Guangxi 541199, China. w19831120@126.com.|Department of Endocrinology and Metabolism, The Second Affiliated Hospital of Guilin Medical University, Guangxi, China.|Center of Diabetic Systems Medicine, Guilin Medical University, Guangxi, China.|Department of Endocrinology and Metabolism, Affiliated Hospital of Guilin Medical University, Guangxi, China.
authors.forename: Tianpeng
authors.initials: T
authors.lastname: Zheng
authors.affiliation: Diabetic Centre of Control and Prevention, The People's Liberation Army 520 Hospital, Sichuan, China.
authors.forename: Yihong
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Medical Examination Center, Affiliated Hospital of Guilin Medical University, Guangxi, China.
authors.forename: Shenghua
authors.initials: S
authors.lastname: Qin
authors.affiliation: Department of Laboratory Medicine, Affiliated Hospital of Guilin Medical University, Guangxi, China.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Endocrinology and Metabolism, Affiliated Hospital of Guilin Medical University, Guangxi, China.
authors.forename: Liuxue
authors.initials: L
authors.lastname: Yang
authors.affiliation: Center of Diabetic Systems Medicine, Guilin Medical University, Guangxi, China.
authors.forename: Xiaoxi
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Psychiatry, Affiliated Hospital of Guilin Medical University, Guangxi, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Psychiatry, Affiliated Hospital of Guilin Medical University, Guangxi, China.|Department of Neurology, Affiliated Hospital of Guilin Medical University, Guangxi, China.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Li
mesh_terms: D000368:Aged; D002097:C-Reactive Protein / Q000378:metabolism; D002681:China; D003430:Cross-Sectional Studies; D003866:Depressive Disorder / Q000201:enzymology* / Q000453:epidemiology*; D018819:Dipeptidyl Peptidase 4 / Q000097:blood*; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D009478:Neuropeptide Y / Q000097:blood; D016017:Odds Ratio; D012307:Risk Factors; D013223:Statistics as Topic
chemical_list: D018836:Inflammation Mediators; D015850:Interleukin-6; D009478:Neuropeptide Y; D002097:C-Reactive Protein; C042807:DPP4 protein, human; D018819:Dipeptidyl Peptidase 4