Background. The relation between low-grade inflammation and metabolic dysfunction in obesity is not fully explored.
Objectives. To evaluate immune parameters in the obese state and after a lifestyle intervention program.
Methods. Patients with obesity (n=87) from an academic obesity clinic were compared to controls with regard to macrophage and T-cell activation (reflected by serum levels of soluble CD163 (sCD163) and soluble IL-2 receptor (sIL-2R), respectively), regulatory T-cells (Treg), and an array of cytokines, chemokines and growth factors. Additionally, in 27 patients the effect of a 75-week lifestyle intervention (dietary advice, exercise and psychoeducation) on these parameters was studied.
Results. Mean sIL-2R and sCD163 levels were higher in patients than controls (sIL-2R:2884±936 pg/mL versus 2207±813 pg/ml, p=0.001; sCD163:1279±580 pg/ml versus 661±271 pg/ml, p<0,0001 respectively). Patients with metabolic syndrome (MetS) had higher sCD163 than those without (1467±656 pg/mL versus 1103±438 pg/mL). Patients had higher IL-1β, IL-1RA, IL-2, IL-4, IL-5, IL-6, IL-8, IL-9, IL-10, IL-15, IL-17A, MCP-1/CCL2, MIP-1α/CCL3, MIP-1β/CCL4, G-CSF, GM-CSF, FGF, IFN-γ, and TNF-α than controls, whereas VEGF-A, PDGF-BB and eotaxin were lower.

Upon intervention, sIL-2R decreased while peripheral Treg frequencies increased (p=0,042 and p=0,005 respectively). The sIL-2R decrease correlated to a decrease in waist circumference (rho=0,388, p=0.045) and in trend to a decrease in MetS components (rho=0.345, p=0,078). The Treg increase was unrelated to weight loss or metabolic improvement. Mean sCD163 did not change significantly upon intervention, nor did the cytokines, chemokines, and growth factors (except IP-10).

Conclusions: A lifestyle intervention improves T-cell homeostasis in obesity. Immunologic alterations can occur independently of metabolic improvement.