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

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.

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.

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.

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