Apolipoprotein E Pittsburgh variant is not associated with the risk of late-onset Alzheimer's disease in a Spanish population

The objective of this study was to assess whether the APOE(Pittsburgh) variant (APOE*4P) is associated to Alzheimer's disease (AD) in a population from Madrid (Spain). APOE*4P variant is caused by an exonic mutation which results in the substitution of proline-28 for leucine-28, only present in APOE*4 alleles. A study in a US population associated this APOE variant with an increased risk for AD, about five times higher than the risk attributed to APOE*4 carriers overall. One hundred and seventeen cases of late-onset AD and 121 matched control subjects from Madrid (Spain) were included. We studied the APOE polymorphism and the APOE*4P occurrence, by PCR and restriction analysis, and plasma lipids levels using standard protocols. As expected, APOE*4 was significantly overrepresented in AD cases. The APOE*4P mutation was observed in heterozygous state in four subjects, two AD (1.71%) and two controls (1.65%). APOE*4P did not confer higher risk for AD, globally (odds ratio 0.14; 95% confidence interval (CI) 0.02-1.12) or respect to APOE*4 carriers (odds ratio 0.14; 95% CI 0.02-1.24). There were no differences in plasma lipids levels among genotype groups. The mutation frequency in controls was higher in our sample than in the US one (1.65 and 0.18%, respectively; Fisher test P=0.049). Our results suggest that this variant is not so uncommon in our population and is not directly related to AD, contrary to what has been proposed for other populations. (C) 2003 Wiley-Liss, Inc.