title: Age-related modifications of circadian rhythm of serum leptin in healthy men.
abstract: BACKGROUND
  Leptin, the product of the ob gene, is secreted by the adipocyte and is involved in the regulation of body weight, energy homeostasis and a wide spectrum of biological activities.
  
  
  OBJECTIVE
  We studied how variations in circadian serum leptin levels change as people age.
  
  
  METHODS
  Serum leptin levels were studied on a circadian basis in 26 men, 6 overweight (BMI >27.8) and 20 with normal weight. The normal-weight men were divided into four age groups: (A) in their 30s, (B) in their 40s, (C) in their 50s, and (D) in their 60s. Serum samples were drawn at 2-hour intervals from 8:00 to 22:00 and hourly from 22:00 to 8:00 for a total of 24 h.
  
  
  RESULTS
  A significant circadian variation of leptin levels was found whatever the age with a peak at night and a trough around noon. The circadian leptin levels were higher in the older normal-weight groups (50s and 60s) and in the groups with a BMI >27.8.
  
  
  CONCLUSIONS
  Our study demonstrates that changes in the characteristics of the circadian rhythm of serum leptin in healthy men are associated with both advancing age and increased BMI.
authors.affiliation: Anti-Senility Research Center of Shandong, Shandong Academy of Medical Sciences, Jinan, People's Republic of China.
authors.forename: Zi-Yan
authors.initials: ZY
authors.lastname: Zhao
authors.forename: Yue-Rong
authors.initials: YR
authors.lastname: Fu
authors.forename: Xin-Hua
authors.initials: XH
authors.lastname: Li
authors.forename: Yu-Yang
authors.initials: YY
authors.lastname: Li
authors.forename: André
authors.initials: A
authors.lastname: Bogdan
authors.forename: Yvan
authors.initials: Y
authors.lastname: Touitou
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002940:Circadian Rhythm / Q000502:physiology*; D006801:Humans; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood*
chemical_list: D015415:Biomarkers; D020738:Leptin