Zinc and platelet membrane microviscosity in Alzheimer's disease. The in vivo effect of zinc on platelet membranes and cognition.

Objectives. To investigate the effects of oral zinc supplementation on: ( i ) plasma zinc concentrations; ( ii ) platelet membrane microviscosity in vivo; and ( iii ) cognitive function of Alzheimer's disease (AD) patients. Design. An open-labelled pilot study. Setting. University of Stellenbosch Medical School and Stikland Hospital. Subjects. Six volunteer AD patients. Outcome measures. Plasma zinc levels, platelet membrane microviscosity and cognition (MMSE and ADAS-cog tests). Results. Oral zinc supplementation (30 mg/day) did not increase plasma zinc levels significantly, but signfficantly increased platelet membrane microviscosity ( P = 0.02; 6 patients). Four patients. who underwent 12 months of evaluation, showed modest cognitive improvement on psychomebic testing (Mini-Mental State Examination and the cognitive portion of the Alzheimer's Disease Assessment scale scores). Conclusions. While earlier literature promoted the use of zinc in AD patients, a recent study has contradicted this and implicated zinc in the aetiology of Alzheimer's disease. On the basis of the above resutts, it may be premature to single out zinc as a causal agent in AD.