OBJECTIVE-YKL-40 is produced by macrophages, and plasma YKL-40 is elevated in patients with diseases characterized by inflammation. In the present study, YKL-40 was examined in relation to obesity, inflammation, and type 2 diabetes.RESEARCH DESIGN AND METHODS-Plasma YKL-40 and adipose tissue YKL-40 mRNA levels were investigated in 199 subjects who were divided into four groups depending on the presence or absence of type 2 diabetes and obesity. In addition, plasma YKL-40 was examined in healthy subjects during a hyperglycemic clamp, in which the plasma glucose level was kept at 15 mmol/l for 3 h, and during a hyperinsulinemiceuglycemic clamp. -40 (76.7 vs. 45.1 ng/ml, P ϭ 0.0001) but not higher expression in adipose tissue YKL-40 mRNA (1.20 vs. 0.98, P ϭ 0.2) compared with subjects with a normal glucose tolerance. Within the groups with normal glucose tolerance and type 2 diabetes, obesity subgroups showed no difference with respect to either plasma YKL-40 or adipose tissue YKL-40 mRNA levels. Multivariate regression analysis showed that plasma YKL-40 was associated with fasting plasma glucose ( ϭ 0.5, P ϭ 0.0014) and plasma interleukin (IL)-6 ( ϭ 0.2, P ϭ 0.0303). Plasma YKL-40 was not related to parameters of obesity. There were no changes in plasma YKL-40 in healthy subjects during either hyperglycemic or hyperinsulinemic-euglycemic clamps.
RESULTS-Patientswith type 2 diabetes had higher plasma YKLCONCLUSIONS-Plasma YKL-40 was identified as an obesityindependent marker of type 2 diabetes related to fasting plasma glucose and plasma IL-6 levels. Diabetes 57:3078-3082, 2008