Two protective genetic pathways may converge to reduce Alzheimer's disease risk

Alzheimer's disease is the most prevalent form of dementia globally. While the APOE ε4 allele stands as the strongest genetic risk factor for late-onset Alzheimer's, the presence of other genetic factors further modifies the risk. In recent years, PLCG2 has emerged as an important protective gene linked to the disease. Two new studies, published in Alzheimer's Research & Therapy and Nature Genetics respectively, have sought to understand how protective PLCG2 variants influence Alzheimer's risk and how APOE genotype shapes the disease's genetic architecture.

Both studies utilized extensive data from various international cohorts, revealing that PLCG2 variants P522R and 3 UTR were linked to a later age of onset for Alzheimer's, particularly among those carrying an APOE ε4 allele. Notably, carriers of the PLCG2-P522R variant exhibited a significantly reduced risk of developing Alzheimer's and experienced onset at a later age.

The PLCG2-P522R variant also correlated with elevated levels of the neuroprotective hormone ghrelin, hinting at additional mechanisms that may enhance disease resilience. Beyond PLCG2, the Nature Genetics study uncovered a protective DDHD1 variant, found to be particularly beneficial for APOE ε4 carriers. DDHD1 is involved in lipid and phospholipid metabolism, and its protective variant was associated with reduced DDHD1 expression in human brain tissue.

The convergence of PLCG2 and DDHD1 variants, both involved in lipid metabolic pathways, suggests that enhanced PLCγ2 signaling may mitigate the detrimental impacts of APOE ε4, promoting resilience against neurodegeneration. These findings open new avenues for research into the interconnected genetic mechanisms underlying Alzheimer's disease.