title: Serum FGF21 levels are increased in obesity and are independently associated with the metabolic syndrome in humans.
abstract: OBJECTIVE
  Fibroblast growth factor 21 (FGF21) is a metabolic regulator with multiple beneficial effects on glucose homeostasis and insulin sensitivity in animal models. This study aimed to investigate the relationship between its serum levels and various cardiometabolic parameters in humans.
  
  
  METHODS
  A newly developed immunoassay was used to measure serum FGF21 levels in 232 Chinese subjects recruited from our previous cross-sectional studies. The mRNA expression levels of FGF21 in the liver and adipose tissues were quantified by real-time PCR.
  
  
  RESULTS
  Serum FGF21 levels in overweight/obese subjects were significantly higher than in lean individuals. Serum FGF21 correlated positively with adiposity, fasting insulin, and triglycerides but negatively with HDL cholesterol, after adjusting for age and BMI. Logistic regression analysis demonstrated an independent association between serum FGF21 and the metabolic syndrome. Furthermore, the increased risk of the metabolic syndrome associated with high serum FGF21 was over and above the effects of individual components of the metabolic syndrome. Our in vitro study detected a differentiation-dependent expression of FGF21 in 3T3-L1 adipocytes and human adipocytes. In db/db obese mice, FGF21 mRNA expression was markedly increased in both the liver and adipose tissue compared with that in their lean littermates. Furthermore, FGF21 expression in subcutaneous fat correlated well with its circulating concentrations in humans.
  
  
  CONCLUSIONS
  FGF21 is a novel adipokine associated with obesity-related metabolic complications in humans. The paradoxical increase of serum FGF21 in obese individuals, which may be explained by a compensatory response or resistance to FGF21, warrants further investigation.
authors.affiliation: Department of Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, China.
authors.forename: Xinmei
authors.initials: X
authors.lastname: Zhang
authors.forename: Dennis C Y
authors.initials: DC
authors.lastname: Yeung
authors.forename: Michal
authors.initials: M
authors.lastname: Karpisek
authors.forename: David
authors.initials: D
authors.lastname: Stejskal
authors.forename: Zhi-Guang
authors.initials: ZG
authors.lastname: Zhou
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Rachel L C
authors.initials: RL
authors.lastname: Wong
authors.forename: Wing-Sun
authors.initials: WS
authors.lastname: Chow
authors.forename: Annette W K
authors.initials: AW
authors.lastname: Tso
authors.forename: Karen S L
authors.initials: KS
authors.lastname: Lam
authors.forename: Aimin
authors.initials: A
authors.lastname: Xu
mesh_terms: D000818:Animals; D044466:Asian People; D015992:Body Mass Index; D002681:China; D004797:Enzyme-Linked Immunosorbent Assay; D005346:Fibroblast Growth Factors / Q000097:blood* / Q000235:genetics; D005951:Glucose Tolerance Test; D006801:Humans; D008322:Mammals; D024821:Metabolic Syndrome / Q000097:blood*; D009765:Obesity / Q000097:blood*; D012333:RNA, Messenger / Q000235:genetics; D012016:Reference Values; D012680:Sensitivity and Specificity
chemical_list: D012333:RNA, Messenger; C414620:fibroblast growth factor 21; D005346:Fibroblast Growth Factors