Relationship Between Serum IL-12 and p40 Subunit Concentrations and Lipid Parameters in Overweight and Obese Women.

Background: Obesity is a chronic low-grade inflammatory state associated with the development of insulin resistance, type 2 diabetes mellitus, and atherosclerosis. Interleukin-12 (IL-12) is a proinflammatory cytokine composed of a 40-kD (p40) subunit and a 35-kD (p35) subunit. p40 might have an independent role in initiating the immune response. Recent findings indicate that IL-12 could be involved in the development of obesity-associated co-morbidities, especially atherosclerosis. It is unclear if there are alternations in circulating concentrations of total IL-12 and its subunit p40 in young subjects with increased adiposity without overt metabolic disturbances. The aim of the present study was to estimate serum total IL-12 together with its p40 subunit in young overweight and obese women and to investigate the associations of these parameters with insulin sensitivity and serum lipids.

Methods: We studied 77 healthy women (37 lean and 40 obese or overweight). Anthropometric measurements, blood biochemical analyses, determination of serum IL-12, IL-12p40 concentrations, and euglycemic-hyperinsulinemic clamp were performed.

Results: We demonstrated an increase in serum p40 in obese subjects (P=0.029). We found positive correlations between p40 and fat mass (r=0.24, P=0.04) and significant negative associations with high-density lipoprotein cholesterol (HDL-C) (r=-0.27, P=0.002). Detectable concentrations of serum IL-12 were observed in 55% of subjects. Individuals with detectable serum concentrations of IL-12 had significantly higher levels of serum triglycerides (P=0.049). A significant association between IL-12 and serum total cholesterol (r=0.32, P=0.042) was observed in this subgroup. No association between p40 or IL-12 and insulin sensitivity was found.

Conclusions: Our data indicate that the IL-12/IL-12p40 system may be associated with lipid abnormalities in obese subjects.