The role of peroxisome proliferator-activated receptor-γ (PPARγ) in Alzheimer's disease

Alzheimer's disease is a complex neurodegenerative disorder, with aging, genetic and environmental factors contributing to its development and progression. The complexity of Alzheimer's disease presents substantial challenges for the development of new therapeutic agents. Alzheimer's disease is typified by pathological depositions of beta-amyloid peptides and neurofibrillary tangles within the diseased brain. It has also been demonstrated to be associated with a significant microglia-mediated inflammatory component, dysregulated lipid homeostasis and regional deficits in glucose metabolism within the brain. The peroxisome proliferator-activated receptor-gamma (PPAR gamma) is a prototypical ligand-activated nuclear receptor that coordinates lipid, glucose and energy metabolism, and is found in elevated levels in the brains of individuals with Alzheimer's disease. A recently appreciated physiological function of this type of receptor is its ability to modulate inflammatory responses. In animal models of Alzheimer's disease, PPAR gamma agonist treatment results in the reduction of amyloid plaque burden, reduced inflammation and reversal of disease-related behavioural impairment. In a recent phase II clinical trial, the use of the PPAR gamma agonist rosiglitazone was associated with improved cognition and memory in patients with mild to moderate Alzheimer's disease. Thus, PPAR gamma may act to modulate multiple pathophysiological mechanisms that contribute to Alzheimer's disease, and represents an attractive therapeutic target for the treatment of the disease.