It is always a good idea to look closely at the biochemistry involved in any potential Alzheimer's disease therapy that shows promise in mouse models. There is perhaps more uncertainty for Alzheimer's than most other age-related conditions when it comes to the degree to which the models are a useful representation of the disease state in humans - which might go some way towards explaining the promising failures that litter the field. In the research here, the authors are aiming to suppress a step in the generation of amyloid-β, one of the proteins that aggregates in growing amounts and is associated with brain cell death in Alzheimer's disease. They achieve this goal using gene therapy to increase the level of PGC-1α, which in turn reduces the level of an enzyme involved in the production of amyloid-β. Interestingly, increased levels of PGC-1α have in the past been shown to produce modest life extension in mice, along with some of the beneficial effects to health associated with calorie restriction.
Current therapies for Alzheimer's disease (AD) are symptomatic and do not target the underlying amyloid-β (Aβ) pathology and other important hallmarks including neuronal loss. PPARγ-coactivator-1α (PGC-1α) is a cofactor for transcription factors including the peroxisome proliferator-activated receptor-γ (PPARγ), and it is involved in the regulation of metabolic genes, oxidative phosphorylation, and mitochondrial biogenesis. We previously reported that PGC-1α also regulates the transcription of β-APP cleaving enzyme (BACE1), the main enzyme involved in Aβ generation, and its expression is decreased in AD patients. We aimed to explore the potential therapeutic effect of PGC-1α by generating a lentiviral vector to express human PGC-1α and target it to hippocampus and cortex of APP23 transgenic mice at the preclinical stage of the disease.Four months after injection, APP23 mice treated with hPGC-1α showed improved spatial and recognition memory concomitant with a significant reduction in Aβ deposition, associated with a decrease in BACE1 expression. hPGC-1α overexpression attenuated the levels of proinflammatory cytokines and microglial activation. This effect was accompanied by a marked preservation of pyramidal neurons in the CA3 area and increased expression of neurotrophic factors. The neuroprotective effects were secondary to a reduction in Aβ pathology and neuroinflammation, because wild-type mice receiving the same treatment were unaffected. These results suggest that the selective induction of PGC-1α gene in specific areas of the brain is effective in targeting AD-related neurodegeneration and holds potential as therapeutic intervention for this disease.