Plasma YKL-40 - a BMI-independent marker of type 2 diabetes

Abstract

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 mellitus (T2DM).

Research Design and Methods. Plasma YKL-40 and adipose tissue YKL-40 mRNA levels were investigated in 199 subjects divided into four groups depending on the presence or absence of T2DM and obesity. In addition, plasma YKL-40 was examined in healthy subjects during a hyperglycaemic clamp, where the plasma glucose level was kept at 15 mM for 3 hours and during a hyperinsulinaemic euglycaemic clamp.

Results. Patients with T2DM had higher plasma YKL-40 (76.7 vs. 45.1 ng/ml, p = 0.0001), but not higher expression in adipose tissue YKL-40 mRNA (1.20 vs. 0.98, p = 0.2), compared to subjects with a normal glucose tolerance. Within the groups with normal glucose tolerance and T2DM, 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 (β = 0.5, p = 0.0014) and plasma IL-6 (β = 0.2, p = 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 hyperglycaemic or hyperinsulinaemic euglycaemic clamps.

Conclusions. Plasma YKL-40 was identified as an obesity-independent marker of T2DM, related to fasting plasma glucose and plasma IL-6 levels.