title: Serum levels of cathepsin D, sirtuin1, and endothelial nitric oxide synthase are correlatively reduced in elderly healthy people.
abstract: OBJECTIVE
  Nowadays, cathepsins have been reported to be related to aging. The aim of this study is to evaluate the association between serum levels of cathepsin D (CTSD) and human aging.
  
  
  METHODS
  In the present study, we analyzed the serum levels of CTSD and its relation with levels of sirtuin1 (SIRT1) and endothelial nitric oxide synthase (eNOS) activity, which were known having an important role in aging. This study recruited 90 healthy subjects (62 men and 28 women), which were subdivided into three groups with respect to age: young (about 19 years old, n = 30), middle-age (about 40 years old, n = 30), and aged (above 65 years old, n = 30). Altered serum levels of CTSD and SIRT1 were measured by enzyme-linked immunosorbent assay, and eNOS activity was assessed by the conversion of 14(C)-L-arginine to 14(C)-L-citrulline.
  
  
  RESULTS
  Elderly subjects had significantly lower CTSD, SIRT1, and eNOS than younger ones. Serum levels of CTSD were negatively correlated with age. There was a statistically significant positive correlation between serum levels of CTSD, eNOS, and SIRT1.
  
  
  CONCLUSIONS
  This study shows lower serum CTSD values in elderly subjects than in younger subjects. This is the first to demonstrate age-related changes in cathepsin D levels in humans and the association between SIRT1 and eNOS.
authors.affiliation: Department of Gerontology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, No. 600, Yi Shan Road, Shanghai, 200233, People's Republic of China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhong
authors.affiliation: Department of Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA.
authors.forename: Alex F
authors.initials: AF
authors.lastname: Chen
authors.affiliation: Shanghai Sixth People's Hospital Jinshan Branch, No. 147 Health Road, Zhujing Town, Jinshan District, Shanghai, 201500, People's Republic of China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Shanghai Sixth People's Hospital Jinshan Branch, No. 147 Health Road, Zhujing Town, Jinshan District, Shanghai, 201500, People's Republic of China.
authors.forename: Ying-Jia
authors.initials: YJ
authors.lastname: Gu
authors.affiliation: Department of Gerontology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, No. 600, Yi Shan Road, Shanghai, 200233, People's Republic of China. fuguoxiang888@163.com.
authors.forename: Guo-Xiang
authors.initials: GX
authors.lastname: Fu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood; D002402:Cathepsin D / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D052250:Nitric Oxide Synthase Type III / Q000097:blood*; D056564:Sirtuin 1 / Q000097:blood*; D055815:Young Adult
chemical_list: C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D002402:Cathepsin D; D056564:Sirtuin 1
keywords: Aging; Cathepsin D; SIRT1; eNOS