Evidence for Peroxisome Dysfunction to be Important in Alzheimer's Disease is Not Conclusive
Peroxisomes in cells are responsible for helping to maintain oxidative metabolism via making and removing hydrogen peroxide, but are also involved in numerous aspects of lipid metabolism, breaking down or converting various lipids necessary to cell function. They have other, less well mapped functions relating to defense against pathogens. There is some evidence for peroxisome loss to occur with age, for this to be a meaningful cause of further cellular dysfunction. As researchers note here, however, the evidence for forms of peroxisome dysfunction to contribute meaningfully to Alzheimer's disease is suggestive but far from conclusive. As is often the case, the fastest path to clarity would be an approach to restore a more youthful peroxisome function to cells in the brain and elsewhere, and see what happens as a result.
Peroxisomes are dynamic, single-membrane-bound organelles ubiquitously distributed throughout eukaryotic cells, containing abundant oxidases, catalase, and lipid-metabolizing enzymes. Their functions encompass the β-oxidation of very-long-chain fatty acids (VLCFAs), the degradation of branched-chain fatty acids, bile acid synthesis, and the biosynthesis of ether phospholipids - notably plasmalogens. Moreover, via catalase (CAT) and related enzymes, peroxisomes are instrumental in sustaining local reactive oxygen species (ROS) homeostasis.
These functions are of particular relevance to the nervous system, where membrane lipid composition, myelin integrity, synaptic plasticity, and redox homeostasis are intimately interconnected. Consequently, peroxisomal dysfunction may simultaneously impair multiple facets of neural cell physiology. Within the central nervous system, peroxisomes establish an integrated metabolic network with the endoplasmic reticulum, mitochondria, lipid droplets, and lysosomes. Thus, peroxisomal abnormalities can concurrently disrupt membrane architecture, energy metabolism, reactive oxygen species (ROS) signaling, and inflammatory responses.
Reduced plasmalogen levels, diminished peroxisomal enzyme activities, enhanced lipid peroxidation, and elevated oxidative stress have been consistently documented in both Alzheimer's disease (AD) brain tissue and animal models. Furthermore, peroxisome-regulated nuclear receptors - particularly the peroxisome proliferator-activated receptors (PPARs) - are closely intertwined with lipid metabolism, insulin sensitivity, inflammatory suppression, and mitochondrial function, rendering them promising targets for drug repurposing and novel therapeutic discovery.
Current evidence does not establish peroxisomal dysfunction as a necessary, sufficient, or universal cause of AD; it is more defensibly viewed as a context-dependent vulnerability, amplifier, or response within reciprocal metabolic-proteinopathy networks. PPAR agonism, lipid modulation, pexophagy regulation, and restoration of peroxisome-mitochondria communication remain investigational. Translation requires longitudinal human evidence, validated target-engagement biomarkers, and adequately powered trials in biologically defined populations. Peroxisomal biology therefore provides a testable framework for studying lipid-redox-organelle interactions in AD, while substantial uncertainty remains regarding temporal precedence, causal magnitude, and therapeutic tractability.