title: Allograft inflammatory factor 1 (AIF-1) is a new human adipokine involved in adipose inflammation in obese women.
abstract: BACKGROUND
  Allograft inflammatory factor 1 (AIF-1) is a putative obesity gene. Our aim was to examine the expression of AIF-1 in human white adipose tissue (WAT) in relation to obesity and metabolic phenotypes in women.
  
  
  METHODS
  WAT secretion of AIF-1 was determined in subcutaneous adipose tissue pieces in vitro by ELISA from 5 subjects. mRNA expression of AIF-1 was determined by RT-qPCR in the isolated cell fractions of adipose tissue (n = 5-6 per group), in subcutaneous and visceral WAT pieces from non-obese (n = 12) and obese women (n = 23), and in some subcutaneous WAT also before and after weight reduction (n = 10). Finally, adipose AIF-1 mRNA was related to metabolic phenotypes in 96 subjects with a wide range of BMI.
  
  
  RESULTS
  AIF-1 was secreted in a time dependent fashion from WAT. The major source of AIF-1 was WAT resident macrophages. Expression of AIF-1 was similar in visceral and subcutaneous WAT and was two-fold increased in obese women (P < 0.01). AIF-1 mRNA expression levels were normalized after weight reduction (P < 0.01). Expression of AIF-1 was inversely correlated with insulin sensitivity as assessed by insulin tolerance test (KITT), and circulating levels of adiponectin (P = 0.02), and positively correlated with insulin resistance as estimated by HOMA (=0.0042).
  
  
  CONCLUSIONS
  AIF-1 is a novel adipokine produced mainly by macrophages within human WAT. Its expression is increased in obese women and associates with unfavourable metabolic phenotypes. AIF-1 may play a paracrine role in the regulation of WAT function through cross-talk between macrophages and other cell types within the adipose tissue.
authors.affiliation: Department of Medicine Huddinge, Lipid Laboratory, Novum, Karolinska Institutet, Karolinska University Hospital, SE-141 86 Huddinge, Stockholm, Sweden. Silvia.Lorente-Cebrian@ki.se.
authors.forename: Silvia
authors.initials: S
authors.lastname: Lorente-Cebrián
authors.forename: Pauline
authors.initials: P
authors.lastname: Decaunes
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Dungner
authors.forename: Anne
authors.initials: A
authors.lastname: Bouloumié
authors.forename: Peter
authors.initials: P
authors.lastname: Arner
authors.forename: Ingrid
authors.initials: I
authors.lastname: Dahlman