Low platelet iPLA2 activity predicts conversion from mild cognitive impairment to Alzheimer's disease: a 4-year follow-up study

Reduced phospholipase A(2) (PLA(2)) activity has been reported in the brain and in blood cells of patients with Alzheimer's disease (AD). Individuals with mild cognitive impairment (MCI) are at increased risk of developing AD. In the present study, we determined the activity of distinct PLA(2) subgroups (iPLA(2), sPLA(2) and cPLA(2)) in older adults with MCI as compared to patients with mild dementia due to AD and to cognitively healthy controls. We investigated whether decreased PLA(2) activity at baseline is associated with the progression of MCI to AD upon follow-up during a period of 4 years. The activity of PLA(2) subgroups was determined in platelets from 169 elderly adults. Progression of MCI to AD was ascertained by standard clinical criteria for AD upon follow-up. At baseline, iPLA(2) activity was significantly decreased (p = 0.001) in patients with AD and MCI as compared to controls. Patients with MCI who progressed to AD during follow-up showed significantly lower iPLA(2) activity at baseline as compared to patients with MCI who did not progress to AD (p = 0.009). Moreover, subjects from the control group at baseline who progressed to MCI during follow-up had lower sPLA(2) and cPLA(2) (p = 0.014 and p = 0.009, respectively). Our findings suggest that low platelet iPLA(2) activity may be a risk marker for AD in subjects with MCI. Moreover, low sPLA(2) and cPLA(2) were related to cognitive decline in healthy controls, suggesting a relationship with the very early stages of the disease.