Activation of PPARα by gemfibrozil lowers tau-associated neuropathology in the MAPT mouse model of Alzheimer's disease.

The current dogma states that inhibiting tau accumulation and its associated neuropathologies might be a relevant strategy to prevent neuronal loss and cognitive dysfunction in Alzheimer's disease (AD). The present study demonstrates the therapeutic potential of an FDA-approved lipid lowering drug and an agonist of peroxisome proliferator and activated receptor α (PPARα), called gemfibrozil, in reducing tau accumulation and associated neuropathologies in the MAPT (PS19) mouse model of AD, expressing P301S mutated form of human tau protein in neurons. Daily oral treatment of gemfibrozil in MAPT mice reduced total tau and phosphorylated form of tau in the hippocampal subregions including CA1 and DG. Concurrently, gemfibrozil treatment upregulated PPARα level in the hippocampus and that was accompanied with inhibition of microgliosis and astrogliosis. Gemfibrozil also attenuated the loss of synaptic plasticity as determined by the expression of post-synaptic protein, PSD95, and calcium influx in the hippocampal tissue. The instrumental role of PPARα in gemfibrozil-mediated reduction of tauopathy was confirmed as PPARα deficiency in MAPT mice significantly augmented tau and phospho-tau accumulation in the hippocampus and gemfibrozil treatment failed to reverse tau pathology and gliosis in the brain of PPARα deficient MAPT mice. Lastly, gemfibrozil improved the cognitive function of MAPT mice during the symptomatic phase of disease progression, but it failed to reverse cognitive impairment in the PPARα deficient MAPT mice. These data suggest that neuroprotective effects of gemfibrozil in MAPT mice is mediated by PPARα. Moreover, targeting PPARα by small molecules like gemfibrozil may hold translational potential against tauopathy.