Analogues, ageing and aberrant assimilation of vitamin B12 in Alzheimer's disease

Vitamin B12 assimilation might be disrupted in patients with Alzheimer's di sease. We therefore measured B12 carrier protein saturation and inactive B1 2 'analogues' in patients compared with healthy elderly individuals in a pr ospective case-controlled survey, Twenty-three patients, aged 60 or over, w ith features compatible with DSM-IV criteria for primary degenerative demen tia of the Alzheimer type were recruited together with 18 cognitively intac t age-matched control subjects. Total vitamin B12 (active corrinoids), holo - and apo-haptocorrin and transcobalamin were measured in serum. B12 analog ues (inactive corrinoids) were estimated from the difference between R-bind er-determined corrinoids and an intrinsic factor based B12 assay. Alzheimer patients had significantly lower active corrinoid than control subjects a nd the analogue/corrinoid ratio was significantly higher in the Alzheimer g roup. The inter-relationship between age, analogues and transcobalamin pola rised patients into two distinct groups. Two disparate mechanisms might exi st for the development of cerebral B12 deficiency in Alzheimer's disease, a lthough both imply a disruption of selective B12 assimilation and analogue elimination in such patients. Copyright (C) 2001 S. Karger AG, Basel.