title: Site-specific circadian expression of leptin and its receptor in human adipose tissue.
abstract: BACKGROUND
  Circadian variability of circulating leptin levels has been well established over the last decade. However, the circadian behavior of leptin in human adipose tissue remains unknown. This also applies to the soluble leptin receptor.
  
  
  OBJECTIVE
  We investigated the ex vivo circadian behavior of leptin and its receptor expression in human adipose tissue (AT).
  
  
  METHODS
  Visceral and subcutaneous abdominal AT biopsies (n = 6) were obtained from morbid obese women (BMI ≥ 40 kg/m²). Anthropometric variables and fasting plasma glucose, leptin, lipids and lipoprotein concentrations were determined. In order to investigate rhythmic expression pattern of leptin and its receptor, AT explants were cultured during 24-h and gene expression was analyzed at the following times: 08:00, 14:00, 20:00, 02:00 h, using quantitative real-time PCR.
  
  
  RESULTS
  Leptin expression showed an oscillatory pattern that was consistent with circadian rhythm in cultured AT. Similar patterns were noted for the leptin receptor. Leptin showed its achrophase (maximum expression) during the night, which might be associated to a lower degree of fat accumulation and higher mobilization. When comparing both fat depots, visceral AT anticipated its expression towards afternoon and evening hours. Interestingly, leptin plasma values were associated with decreased amplitude of LEP rhythm. This association was lost when adjusting for waist circumference.
  
  
  CONCLUSIONS
  Circadian rhythmicity has been demonstrated in leptin and its receptor in human AT cultures in a site-specific manner. This new knowledge paves the way for a better understanding of the autocrine/paracrine role of leptin in human AT.
authors.affiliation: Department of Physiology, Faculty of Biology, University of Murcia, Murcia, Spain.
authors.forename: P
authors.initials: P
authors.lastname: Gómez Abellán
authors.forename: C
authors.initials: C
authors.lastname: Gómez Santos
authors.forename: J A
authors.initials: JA
authors.lastname: Madrid
authors.forename: F I
authors.initials: FI
authors.lastname: Milagro
authors.forename: J
authors.initials: J
authors.lastname: Campion
authors.forename: J A
authors.initials: JA
authors.lastname: Martínez
authors.forename: J A
authors.initials: JA
authors.lastname: Luján
authors.forename: J Ma
authors.initials: JM
authors.lastname: Ordovás
authors.forename: M
authors.initials: M
authors.lastname: Garaulet
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000886:Anthropometry; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology*; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D020738:Leptin / Q000096:biosynthesis* / Q000235:genetics; D008055:Lipids / Q000097:blood; D008074:Lipoproteins / Q000097:blood; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D054411:Receptors, Leptin / Q000096:biosynthesis* / Q000235:genetics; D050151:Subcutaneous Fat / Q000378:metabolism; D046509:Tissue Culture Techniques
chemical_list: D001786:Blood Glucose; D020738:Leptin; D008055:Lipids; D008074:Lipoproteins; D054411:Receptors, Leptin; D012313:RNA