Human red blood cell choline uptake with age and Alzheimer's disease

Since previous studies suggested that blood choline homeostasis is altered in aging and in Alzheimer's disease, choline uptake was examined in human red blood cells (RBC) from young adults, intellectually-intact elderly controls and outpatients with Alzheimer's disease. Eadie-Hofstee analysis of uptake by RBC from young controls indicated two components; thus, group comparisons were done with 1 and 50 microM choline in the media. Temperature-dependent choline uptake at low and high choline concentrations increased in RBC from elderly controls (62-66%) or Alzheimer patients (52-54%) compared to young controls. These changes in transport were not directly related to altered RBC choline content, since RBC choline concentrations did not vary significantly between groups. However, plasma choline content was significantly elevated in elderly controls and Alzheimer patients compared to young control values. The RBC to plasma ratio of choline was reduced in elderly compared to young controls, whereas the ratio in Alzheimer patients was between the two other groups. Thus, abnormalities in RBC choline uptake and plasma choline content were not exacerbated in Alzheimer patients, and these results do not support suggestions that Alzheimer's disease is a form of generalized accelerated aging. The striking changes in RBC choline uptake and plasma choline content in elderly subjects do indicate age-related changes in systemic choline homeostasis and these abnormalities may contribute to the predisposition of the elderly to neurological diseases.