This study aimed to determine age-dependent alterations in serum cytokines, peripheral blood mononuclear cell (PBMC) cytokine production, natural killer (NK) cell activity, and urinary 8-epi-prostaglandin F2α (PGF2α). Nine hundred eighty-seven healthy and nonobese subjects were divided into five age groups: 20-34 (group 1), 35-44 (group 2), 45-54 (group 3), 55-64 (group 4), and 65-80 (group 5) years of age. After adjusting for BMI, sex, and smoking and drinking status, serum interferon (IFN)-γ levels decreased in groups 3, 4, and 5 compared with those in groups 1 and 2. Production of IFN-γ by unstimulated PBMCs was lower in the older groups (groups 4 and 5) than in the younger groups (groups 1 and 3). Serum interleukin (IL)-12 was lower in group 5 than in groups 1 and 2. In contrast, both serum and PBMC IL-6 were higher in group 5 than in groups 1, 2, and 3. Urinary 8-epi-PGF2α increased in group 3 compared with that in group 1 and further increased in group 5. Multiple linear regression analysis revealed that serum IFN-γ levels were negatively affected by age, and NK cell activity at a ratio of E:T = 5:1 was positively affected by PBMC IFN-γ. This study shows the age-related reductions in serum and PBMC IFN-γ and serum IL-12 and age-related increases in serum and PBMC IL-6 and oxidative stress in healthy nonobese subjects. Additionally, circulating IL-6 levels may be a better marker of the chronic low-grade inflammatory activity associated with aging than systemic levels of high-sensitivity C-reactive protein, TNF-α, and IL-1β.
Keywords: Aging; Inflammation; NK cell activity; Oxidative stress; PBMC cytokine; Serum cytokine.