Influence of lysosomal acid lipase polymorphisms on chromosome 10 on the risk of Alzheimer's disease and cholesterol metabolism

Linkage analyses have identified a possible hot spot for a late-onset Alzheimer's disease (LOAD) risk gene on chromosome 10q21-22 and 10q25. It was also shown that cholesterol metabolism is involved in the pathogenic mechanisms of AD. The gene of lysosomal acid lipase (LIPA) is located next to the putative hot spot on chromosome 10. Its protein is involved in cholesterol metabolism and responsible for catalysing the hydrolysis of cholesteryl esters and triglycerides inside the lysosome. Previous publications reported controversial results on the role of LIPA polymorphisms on the risk of LOAD. We investigated two LIPA polymorphisms (rs1051338 and rs2297472) for their putative effect on the risk of LOAD in a homogenous sample of German origin. Genotypes of the investigated polymorphisms in AD patients and controls were compared. Also the effect of the LIPA gene polymorphisms on plasma cholesterol levels and 24S-hydroxycholesterol/cholesterol ratios on AD patients were investigated. None of the observed polymorphisms showed a significant influence on the risk of AD. We found that LIPA exon 2 polymorphism (rs1051338) influenced plasma 24S-hydroxycholesterol/cholesterol ratios in AD patients where carriers of the C/C allele presented with higher ratios than heterozygote carriers of the LIPA allele. Even though the biological function and gene location of LIPA on chromosome 10 suggest that LIPA might be a candidate for an AD risk gene, our results revealed that polymorphisms in LIPA did not influence the risk of AD in our study.