title: Is Low Serum Klotho Level Associated with Alterations in Coronary Flow Reserve?
abstract: BACKGROUND
  The Klotho gene, described as an "aging suppressor" gene, encodes a single-pass transmembrane protein. The extracellular part of Klotho is cleaved and released into the circulation where it may function as a vasculoprotective hormone. Coronary flow reserve (CFR) is accepted as a marker of coronary microvascular dysfunction when epicardial coronary stenosis is absent. There are no data regarding the relationship between serum Klotho levels and disorders in coronary microcirculation in healthy adults. We aimed to investigate the association between serum Klotho levels and alterations in coronary microcirculation in healthy adults using echocardiographic measurements of CFR.
  
  
  METHODS
  Thirty-four healthy volunteers (median age: 34 [27-39], 14 males) were enrolled in this study. The study population was divided into two subgroups according to the median value of serum Klotho levels: a high Klotho (HK) group (n = 17, median age: 34 [30-38]; 6 males) and a low Klotho (LK) group (n = 17, median age: 32 [26-39]; 8 males). The analysis of coronary flow velocities was performed by transthoracic Doppler echocardiography.
  
  
  RESULTS
  Hyperemic diastolic peak flow velocities and CFR were significantly higher in the HK group than in the LK group (70 [66-92] versus 61 [47-66], P = 0.003 and 3.0 [2.6-3.8] versus 2.2 [1.7-2.8], respectively, P = 0.001). Serum Klotho levels were positively correlated with CFR (P < 0.001).
  
  
  CONCLUSIONS
  Serum Klotho levels correlate with CFR in a healthy population. Low serum Klotho levels may potentially identify patients with impaired CFR.
authors.affiliation: Department of Cardiology, Istanbul Medeniyet University, Goztepe Training and Research Hospital, Istanbul, Turkey.
authors.forename: Nursen
authors.initials: N
authors.lastname: Keles
authors.affiliation: Department of Cardiology, Istanbul Medeniyet University, Goztepe Training and Research Hospital, Istanbul, Turkey.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Caliskan
authors.affiliation: Department of Family Physicians, Istanbul Medeniyet University, Goztepe Training and Research Hospital, Istanbul, Turkey.
authors.forename: Burcu
authors.initials: B
authors.lastname: Dogan
authors.affiliation: Department of Cardiology, Istanbul Medeniyet University, Goztepe Training and Research Hospital, Istanbul, Turkey.
authors.forename: Feyza
authors.initials: F
authors.lastname: Aksu
authors.affiliation: Department of Cardiology, Istanbul Medeniyet University, Goztepe Training and Research Hospital, Istanbul, Turkey.
authors.forename: Serkan
authors.initials: S
authors.lastname: Bulur
authors.affiliation: Department of Neurology, Uskudar Government Hospital, İstanbul, Turkey.
authors.forename: Necibe Nur
authors.initials: NN
authors.lastname: Keles
authors.affiliation: Department of Internal Medicine, Istanbul Medeniyet University, Goztepe Training and Research Hospital, Istanbul, Turkey.
authors.forename: Osman
authors.initials: O
authors.lastname: Kostek
authors.affiliation: Department of Cardiology, Fatih University, Istanbul, Turkey.
authors.forename: Soe Moe
authors.initials: SM
authors.lastname: Aung
authors.affiliation: Department of Biochemistry, Istanbul Medeniyet University, Goztepe Training and Research Hospital, Istanbul, Turkey.
authors.forename: Banu
authors.initials: B
authors.lastname: Isbilen
authors.affiliation: Department of Cardiology, Istanbul Medeniyet University, Goztepe Training and Research Hospital, Istanbul, Turkey.
authors.forename: Kenan
authors.initials: K
authors.lastname: Demircioglu
authors.affiliation: Department of Cardiology, Iskilip Atıf Hoca State Hospital, Corum, Turkey.
authors.forename: Macit
authors.initials: M
authors.lastname: Kalcik
authors.affiliation: Department of Internal Medicine, Istanbul Medeniyet University, Goztepe Training and Research Hospital, Istanbul, Turkey.
authors.forename: Aytekin
authors.initials: A
authors.lastname: Oguz
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001783:Blood Flow Velocity; D003324:Coronary Artery Disease / Q000097:blood* / Q000000981:diagnostic imaging*; D003326:Coronary Circulation; D004452:Echocardiography / Q000379:methods; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D005966:Glucuronidase / Q000097:blood*; D006801:Humans; D000090265:Klotho Proteins; D008297:Male; D055806:Microvessels / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; D005966:Glucuronidase; D000090265:Klotho Proteins
keywords: Klotho; coronary artery disease; coronary flow reserve