title: Cerebrospinal fluid xenin levels during body mass reduction: no evidence for obesity-associated defective transport across the blood-brain barrier.
abstract: BACKGROUND
  Recent studies have shown that xenin can act in the hypothalamus, reducing food intake through a leptin- and melanocortin system-independent mechanism.
  
  
  OBJECTIVE
  To evaluate the impact of body mass reduction on the blood and cerebrospinal fluid (CSF) levels of xenin.
  
  
  METHODS
  Thirteen obese patients (11 women) selected for roux-in-Y gastric bypass surgery were evaluated before and approximately 8 months after surgery. Xenin was determined in serum and CSF by radioimmunoassay.
  
  
  RESULTS
  As compared with lean subjects, obese patients have increased blood levels of xenin, which reduce after surgery. There are significant correlations between blood xenin and blood leptin and insulin levels. CSF concentration of xenin is ∼10-fold lower than blood levels, and is significantly higher in obese subjects as compared with lean ones, returning to normal levels after body mass reduction. There is a significant linear correlation between CSF and blood levels of xenin.
  
  
  CONCLUSIONS
  Xenin is present in the human CSF in a concentration ∼10-fold lower than the blood. Both blood and CSF xenin are correlated with blood levels of important markers of adiposity, leptin and insulin. The levels of CSF xenin are linearly correlated with blood xenin, independently of patient body mass, suggesting that either its transport across the blood-brain barrier is not saturated in the concentration range detected in this study or that there is a coordinated release of xenin from the periphery and the CNS.
authors.affiliation: Laboratory of Cell Signaling, University of Campinas, Campinas, Brazil.
authors.forename: S
authors.initials: S
authors.lastname: van de Sande-Lee
authors.forename: A R
authors.initials: AR
authors.lastname: Cardoso
authors.forename: C R
authors.initials: CR
authors.lastname: Garlipp
authors.forename: E A
authors.initials: EA
authors.lastname: Chaim
authors.forename: J C
authors.initials: JC
authors.lastname: Pareja
authors.forename: B
authors.initials: B
authors.lastname: Geloneze
authors.forename: L A
authors.initials: LA
authors.lastname: Velloso
mesh_terms: D000293:Adolescent; D000328:Adult; D001692:Biological Transport; D015415:Biomarkers; D001812:Blood-Brain Barrier / Q000378:metabolism*; D015992:Body Mass Index; D005215:Fasting / Q000097:blood / Q000134:cerebrospinal fluid*; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D020738:Leptin / Q000097:blood / Q000134:cerebrospinal fluid*; D008297:Male; D008875:Middle Aged; D009496:Neurotensin / Q000097:blood / Q000134:cerebrospinal fluid*; D009767:Obesity, Morbid / Q000097:blood / Q000134:cerebrospinal fluid* / Q000601:surgery; D011863:Radioimmunoassay; D015431:Weight Loss
chemical_list: D015415:Biomarkers; D020738:Leptin; C077659:xenin 25; D009496:Neurotensin