Imaging Links Altered Metabolism and Oxygen Use in Alzheimer’s Disease
Researchers at the University of Virginia have combined two optical imaging techniques to measure cellular metabolism and oxygen levels simultaneously in the living brains of an Alzheimer’s disease mouse model.
- The study utilized two-photon fluorescence lifetime imaging microscopy (FLIM) and phosphorescence lifetime imaging microscopy (PLIM) to observe living brain tissue in mice.
- Results showed that Alzheimer’s model mice had altered mitochondrial metabolic activity and lower oxygen partial pressure in the cortical vascular network compared to wild-type mice.
- The dual-imaging approach allows investigators to capture both energy production and vascular oxygenation at the exact same moment without introducing external fluorescent labels for metabolism.
Researchers Combine FLIM and PLIM to Track Brain Energy
Understanding how brain cells produce and use energy remains a significant challenge in neurological research. Mitochondria supply much of a cell’s energy, but they become dysfunctional in Alzheimer’s disease. At the same time, changes in blood flow and oxygen availability place additional demands on brain tissue. Measurements of oxygen supply or cellular energy production alone do not necessarily reveal what is happening to the other process.
To overcome this hurdle, researchers in Ammasi Periasamy’s group at the University of Virginia combined FLIM and PLIM techniques. FLIM tracks cellular metabolism by measuring how long fluorescent molecules remain in an excited state before releasing light. The team focused on NAD(P)H, a naturally occurring molecule involved in energy production that exists either freely or bound to proteins. The proportion of protein-bound NAD(P)H served as an indicator of mitochondrial metabolic activity. Meanwhile, PLIM provided information about oxygen through an oxygen-sensitive ruthenium-based probe, allowing investigators to estimate the partial pressure of oxygen in the brain’s vascular network.
Synchronized Measurements Reveal Differences in Alzheimer’s Model
Achieving simultaneous measurement required precise synchronization between a Zeiss two-photon microscope and Becker & Hickl lifetime-imaging electronics, according to Dr. Ammasi Periasamy, Professor and Director of the W.M. Keck Center for Cellular Imaging at the University of Virginia. Careful calibration and stable physiological conditions allowed the research team to translate these lifetime signals into reliable readings.
When the anesthetized animals were at rest, the measurements revealed clear differences between the groups. The cortices of the Alzheimer’s disease model mice showed a higher protein-bound fraction of NAD(P)H than healthy, wild-type animals. Simultaneously, oxygen partial pressure in the cortical vascular network was lower in the Alzheimer’s model, which the researchers interpret as evidence of greater oxygen consumption.
Broader Context of Oxygen Metabolism in Neurological Disease
The findings indicate that changes in cellular energy metabolism and oxygen use can be detected concurrently in the living brain. Andrés Norambuena, a senior scientist at the University of Virginia and coauthor of the study, noted that connecting these factors matters because mitochondrial dysfunction and impaired cerebral oxygenation have both been implicated in Alzheimer’s disease yet are often investigated separately.
The role of oxygen metabolism in Alzheimer’s disease has drawn wider scientific interest. A review article published by Guangdong Liu and colleagues in Heliyon outlines how hypoxia, oxidative stress, and mitochondrial dysfunction interact during the pathogenesis of the condition. That review notes that chronic hypoxia aggravates amyloid-beta metabolism and tau phosphorylation, forming a pathological cycle.
Because the current data stem from a mouse model, the imaging patterns do not yet establish whether identical metabolic and oxygen profiles occur in human patients.