Increased circulating and visceral adipose tissue expression levels of YKL-40 in obesity-associated type 2 diabetes are related to inflammation: impact of conventional weight loss and gastric bypass

J Clin Endocrinol Metab. 2011 Jan;96(1):200-9. doi: 10.1210/jc.2010-0994. Epub 2010 Oct 13.


Context: Plasma YKL-40 is elevated in patients with type 2 diabetes. The potential role of visceral adipose tissue (VAT) as a significant source of YKL-40 is unknown.

Objective: In the study circulating and expression levels of YKL-40 were examined in VAT analyzing the contribution of adipocytes and stromovascular fraction cells (SVFCs). We also explored YKL-40's implication in insulin resistance and inflammation and the effect of weight loss on plasma YKL-40 concentrations.

Patients and methods: Samples obtained from 53 subjects were used in the study. Gene and protein expression levels of YKL-40 were analyzed in VAT as well as in both adipocytes and SVFCs. In addition, circulating YKL-40 concentrations were measured before and after weight loss achieved either by Roux-en-Y gastric bypass (n = 26) or after a conventional dietetic program (n = 20).

Results: Circulating concentrations and VAT expression of YKL-40 were increased in obese patients with type 2 diabetes (P < 0.01) as well as associated with variables of insulin resistance and inflammation. No differences in YKL-40 expression levels between adipocytes and SVFCs were detected. Monocyte chemoattractant protein-1 and homeostasis model assessment emerged (P < 0.01) as independent factors predicting circulating YKL-40. Elevated levels of YKL-40 in obese patients decreased after weight loss following a conventional hypocaloric diet (P < 0.05) but not via a surgery-induced negative energy balance mediated by the Roux-en-Y gastric bypass.

Conclusions: The association of increased YKL-40 mRNA and protein levels in VAT with its circulating concentrations indicates an important contribution of VAT in YKL-40 regulation. Furthermore, our data suggest a relevant role of glucose metabolism and inflammation on YKL-40 regulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipocytes / metabolism
  • Adipokines
  • Adult
  • Analysis of Variance
  • Chemokine CCL2 / metabolism
  • Chitinase-3-Like Protein 1
  • Diabetes Mellitus, Type 2 / complications
  • Diabetes Mellitus, Type 2 / metabolism*
  • Diabetes Mellitus, Type 2 / surgery
  • Female
  • Gastric Bypass*
  • Glycoproteins / metabolism*
  • Humans
  • Inflammation / complications
  • Inflammation / metabolism*
  • Inflammation / surgery
  • Insulin Resistance / physiology
  • Intra-Abdominal Fat / metabolism*
  • Intra-Abdominal Fat / surgery
  • Lectins / metabolism*
  • Male
  • Middle Aged
  • Obesity / complications
  • Obesity / metabolism*
  • Obesity / surgery
  • Treatment Outcome
  • Weight Loss / physiology*


  • Adipokines
  • CHI3L1 protein, human
  • Chemokine CCL2
  • Chitinase-3-Like Protein 1
  • Glycoproteins
  • Lectins