Genetic influence on inflammation variables in the elderly

Background - Inflammation variables (C-reactive protein [CRP], fibrinogen, and soluble intercellular adhesion molecule-1 [sICAM-1]) have been identified as risk factors for cardiovascular disease. It is still not known how much the regulation of inflammatory risk factors is determined by genetic factors, and the aim of this study was to determine the heritability of these inflammation variables and of the acute phase regulating cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) at older ages. Methods and Results - The heritability of CRP, fibrinogen, sICAM-1, IL-6, and TNF-alpha was determined in a twin study consisting of 129 monozygotic twin pairs and 153 dizygotic same-sex twins aged 73 to 94 years who participated in the Longitudinal Study of Aging of Danish Twins. Furthermore, we determined the influence of selected genetic polymorphisms on the plasma level variations. Genetic factors accounted for 20% to 55% of the variation in plasma levels of the inflammation variables. The highest heritability was found for sICAM-1. The genetic polymorphisms we studied explained only a small, insignificant part of the heritability. Conclusions - This study in elderly twins provides evidence for a substantial genetic component of inflammatory cardiovascular risk factors among the elderly.