title: Leucocytes are a major source of circulating nicotinamide phosphoribosyltransferase (NAMPT)/pre-B cell colony (PBEF)/visfatin linking obesity and inflammation in humans.
abstract: OBJECTIVE
  Nicotinamide phosphoribosyltransferase (NAMPT) is a multifunctional protein potentially involved in obesity and glucose metabolism. We systematically studied the association between circulating NAMPT, obesity, interventions and glucose metabolism and investigated potential underlying inflammatory mechanisms.
  
  
  METHODS
  Fasting morning NAMPT serum levels were measured in cohorts of lean vs obese children, cohorts of intervention by lifestyle, exercise and bariatric surgery, and during an OGTT. In addition, mRNA expression, protein production and enzymatic activity of NAMPT were assessed from isolated leucocytes and subpopulations.
  
  
  RESULTS
  Circulating NAMPT was significantly elevated in obese compared with lean children and declined after obesity interventions concomitantly with the decline in BMI, high-sensitivity C-reactive protein (hsCrP) and leucocyte counts. Circulating NAMPT significantly correlated with glucose metabolism and cardiovascular variables in univariate analyses, but only the association with glucose response during an OGTT was independent from BMI. We therefore assessed the NAMPT dynamic following an oral glucose load and found a significant decline of NAMPT levels to 77.0 ± 0.1% as a function of time, and insulin-to-glucose ratio during an OGTT in obese insulin-resistant adolescents. Circulating NAMPT was, however, most strongly associated with leucocyte counts (r = 0.46, p < 0.001). The leucocyte count itself determined significantly and independently from BMI insulin resistance in multiple regression analyses. We systematically evaluated NAMPT expression among several tissues and found that NAMPT was predominantly expressed in leucocytes. In subsequent analyses of leucocyte subpopulations, we identified higher NAMPT protein concentrations in lysates of granulocytes and monocytes compared with lymphocytes, whereas granulocytes secreted highest amounts of NAMPT protein into cell culture supernatant fractions. We confirmed nicotinamide mononucleotide enzymatic activity of NAMPT in all lysates and supernatant fractions. In monocytes, NAMPT release was significantly stimulated by lipopolysaccharide (LPS) exposure.
  
  
  CONCLUSIONS
  Leucocytes are a major source of enzymatically active NAMPT, which may serve as a biomarker or even mediator linking obesity, inflammation and insulin resistance.
authors.affiliation: University Hospital for Children & Adolescents, University of Leipzig, Liebigstr. 20A, 04103 Leipzig, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Friebe
authors.forename: M
authors.initials: M
authors.lastname: Neef
authors.forename: J
authors.initials: J
authors.lastname: Kratzsch
authors.forename: S
authors.initials: S
authors.lastname: Erbs
authors.forename: K
authors.initials: K
authors.lastname: Dittrich
authors.forename: A
authors.initials: A
authors.lastname: Garten
authors.forename: S
authors.initials: S
authors.lastname: Petzold-Quinque
authors.forename: S
authors.initials: S
authors.lastname: Blüher
authors.forename: T
authors.initials: T
authors.lastname: Reinehr
authors.forename: M
authors.initials: M
authors.lastname: Stumvoll
authors.forename: M
authors.initials: M
authors.lastname: Blüher
authors.forename: W
authors.initials: W
authors.lastname: Kiess
authors.forename: A
authors.initials: A
authors.lastname: Körner
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D002648:Child; D015444:Exercise / Q000502:physiology; D005260:Female; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D006801:Humans; D007249:Inflammation / Q000097:blood*; D007962:Leukocytes / Q000201:enzymology*; D008297:Male; D054409:Nicotinamide Phosphoribosyltransferase / Q000097:blood* / Q000235:genetics; D009765:Obesity / Q000097:blood*; D056564:Sirtuin 1 / Q000235:genetics
chemical_list: D054409:Nicotinamide Phosphoribosyltransferase; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D005947:Glucose