Age-associated increased interleukin-6 gene expression, late-life diseases, and frailty

Interleukin-6 (IL-6) is a proinflammatory cytokine that is normally tightly regulated and expressed at low levels, except during infection, trauma, or other stress. Among several factors that down-regulate IL-6 gene expressio n are estrogen and testosterone. After menopause or andropause, IL-6 levels are elevated, even in the absence of infection, trauma, or stress. IL-6 is a potent mediator of inflammatory processes, and it has been proposed that the age-associated increase in IL-6 accounts for certain of the phenotypic changes of advanced age, particularly those that resemble chronic inflamma tory disease [decreased lean body mass, osteopenia, low-grade anemia, decre ased serum albumin and cholesterol, and increased inflammatory proteins suc h as C-reactive protein (CRP) and serum amyloid A]. Furthermore, the age-as sociated rise in IL-6 has been linked to lymphoproliferative disorders, mul tiple myeloma, osteoporosis, and Alzheimer's disease. This overview discuss es the data relating IL-6 to age-associated diseases and to frailty. Like t he syndrome of inappropriate antidiuretic hormone, it is possible that cert ain clinically important late-life changes are due to an inappropriate pres ence of IL-6.