Blood pesticide levels linked to Alzheimer’s

Higher serum levels of pesticides could be contributing to a higher risk of developing Alzheimer’s disease, according to a study published online Jan. 27 in JAMA Neurology.

Researchers tested blood serum levels of dichlorodiphenyldichloroethylene (DDE), a metabolite of the banned pesticide dichlorodiphenyltrichloroethane (DDT), and found Alzheimer’s patients to have 3.8 times the DDE of healthy subjects. Results of the study indicated that apolipoprotein E (APOE) allele carriers may be especially sensitive to the neurodegenerative impact of DDE. The pesticide was prevalent from the 1940s through the early 1970s. Athough it was officially taken off the market due to health concerns, traces of it are still in the environment.

Jason R. Richardson, PhD, from the department of environmental and occupational medicine at Rutgers Robert Wood Johnson Medical School, Piscataway, N.J., and colleagues assessed correlations of Alzheimer’s disease, serum levels of DDE and any potential influence of the APOE genotype. Additionally, the researchers evaluated whether DDT or DDE changes the normal behavior of amyloid precursor protein (APP) in cultured neuronal cells.

“To our knowledge, few studies have explored the potential of environmental exposures to contribute to [Alzheimer’s disease], but occupational exposure to metals, solvents, and pesticide is reported to be a potential environmental contributor,” wrote Richardson et al.

For this study, researchers analyzed blood and brain samples collected from 2002 to 2008. Data were analyzed from 79 control samples and 86 samples from patients with Alzheimer’s disease. No other similar pesticides were elevated in the blood of either normal controls or Alzheimer’s patients. At least one APOE allele was found lurking in 35 percent of controls and 65 percent of those with Alzheimer’s. A “significant interaction” between APOE status and DDE levels was found for those who performed poorly on mini-mental state examination.

The results of neuronal cell culture showed that the presence of DDT and DDE increased APP, which could encourage the buildup of amyloid plaques.

“The finding that DDT and DDE increase APP levels in cells provides a mechanistic plausibility to the association between these exposures and AD,” wrote the authors. “If elevation of APP by DDT and/or DDE is confirmed in animal studies and humans, it may provide an avenue for a targeted treatment of individuals with high levels of DDE, such as beta-site APP-cleaving enzyme inhibitors, to prevent cleavage of elevated APP to beta-amyloid 42.”