THE ARISING · Longevity & Healthspan
Vesicles Shed by Mitochondria Carry Microglial Protein Ggt1 Into Alzheimer's Pathology
Tiny packages shed by the brain's mitochondria may help carry Alzheimer's disease from cell to cell, according to a study in Nature Aging. The packages, called mitovesicles, were more abundant in Alzheimer's brains, and they carried a protein called Ggt1 that the researchers tie to the damage.
The work is laboratory research. It used brain tissue from patients with Alzheimer's disease and 5×FAD mice, a standard mouse model of the disease, along with wild-type mice. No treatment has been tested in people.
Mitochondria are the energy-producing structures inside cells. Cells can release mitochondrial components inside extracellular vesicles, small membrane-wrapped packets. Mitovesicles are a recently identified type.
The team found that release of mitovesicles was enriched in brain tissue from patients with Alzheimer's and in 5×FAD mice.
The key experiments tested whether the vesicles could drive disease. Mitovesicles from 5×FAD mouse brains, which the authors call ADmtVs, were administered to wild-type mice. They induced Alzheimer's-like behavioral and pathological changes. The same vesicles accelerated disease progression in mice that already had the Alzheimer's model.
The researchers also examined what controls release. According to the paper, mitovesicle release was regulated by mitochondrial respiratory metabolism. Blocking release significantly alleviated Alzheimer's-like features in the mice.
Proteomic analysis, a survey of the proteins in the vesicles, identified Ggt1 as highly enriched in ADmtVs. Ggt1 is an enzyme that breaks down glutathione, an antioxidant that helps cells manage oxidative stress. Glutathione levels are reduced in the brains of Alzheimer's patients and animals, the authors note. The study describes Ggt1 as a microglial protein, and microglia are the brain's immune cells.
Reducing Ggt1 helped. Inhibiting its expression and activity mitigated Alzheimer's-like features in 5×FAD mice and delayed the disease progression induced by ADmtVs. The authors suggest Ggt1 is a pathological cargo of the vesicles.
For people thinking about brain aging, the finding offers a proposed route linking mitochondrial stress, immune cells and the spread of pathology. The authors say mitovesicles and Ggt1 are potential therapeutic targets. The evidence so far comes from mice and human tissue, so whether the same chain operates in living patients is unknown.
Next to watch is whether other groups reproduce the findings and whether interventions aimed at Ggt1 or vesicle release advance beyond mouse models.