Modulation of apolipoprotein E and interleukin-1β in the aging liver

With aging there is a decline in liver function that includes reductions in hepatic blood flow, metabolite clearance, and impaired tissue repair following injury. An increase in inflammatory signaling is often observed during aging, with inflammation potentially mediating age-related changes in the liver. Apolipoprotein E (ApoE) is primarily produced by the liver and has been shown to possess anti-inflammatory properties in a variety of paradigms and experimental settings. In the present study, we correlated age-related alterations in ApoE expression with age-related changes in the cytokine interleukin-1 beta (IL-1β), in the liver of rats of increasing age. A significant increase in ApoE mRNA, and a significant decrease in IL-1β mRNA, was seen with increasing age. At the protein level, ApoE expression increased with aging, although IL-1β expression remained constant. No correlation was found between ApoE and IL-1β expression at the mRNA or protein level. Taken together, these studies demonstrate that ApoE expression is altered during normal aging, and indicates that there is no correlation between ApoE and IL-1β expression in the aging liver.