Investigations of a CA repeat in the oestrogen receptor β gene in patients with Alzheimer's disease

Several studies have shown that oestrogen treatment after menopause decreases the risk for Alzheimer's disease (AD). It is also known that oestrogen stimulates the outgrowth of nerve cells and that apolipoprotein E (Apo E) synthesis and amyloid precursor protein (APP) metabolism are regulated by oestrogen. Recently a new oestrogen receptor was identified, oestrogen receptor β (ERβ), located at chromosome 14q22-24. Several genes close to this chromosomal region have been implicated in AD, but the results are conflicting. Our hypothesis was that variations in the ERβ gene could be the underlying cause to the positive findings in these genes and we have therefore investigated a CA repeat¹ in intron 5 of the ERβ gene. Three hundred and thirty-six AD cases and 110 healthy age-matched controls were included in this study. Fourteen different alleles were found with frequencies between 0.1 and 37%. There was no significant difference between AD cases and controls when all alleles were compared. However, allele 5 was seen in 13.6% of the controls but only in 8.0% of AD cases (P=0.014; odds ratio (OR)=0.55). No AD patient homozygous for this allele was seen but three controls were homozygous. In conclusion, our findings suggest the ERβ allele 5 to be a protective factor. However, this has to be confirmed in a larger population.