Alzheimer’s disease is best known for its effects on memory and cognition, but the disease also involves changes in how brain cells produce and use energy. Mitochondria, the structures that supply much of a cell’s energy, can become dysfunctional in Alzheimer’s disease. At the same time, changes in blood flow and oxygen availability may place additional demands on brain tissue. Understanding how these processes interact could help researchers characterize metabolic changes that accompany the disease.
A recent study published in Neurophotonics examines these processes together in the living brain. Researchers in Ammasi Periasamy ’s group at the University of Virginia (UVA) combined two forms of two-photon lifetime microscopy to measure cellular metabolism and oxygen levels in the cerebral cortex of mice. They compared Alzheimer’s disease mouse model with healthy, wild-type mice.
The approach addresses an important difficulty in studying brain metabolism. Oxygen supply and cellular energy production are closely related, but measurements of one do not necessarily reveal what is happening to the other. By collecting both types of information at the same time, the researchers could examine how metabolic activity relates to oxygen availability within the same living tissue.
Measuring metabolism through autofluorescence
To track cellular metabolism, the team used two-photon fluorescence lifetime imaging microscopy, or FLIM. Rather than simply measuring the brightness of fluorescence, FLIM measures how long fluorescent molecules remain in an excited state before releasing light.
The researchers focused on NAD(P)H, a naturally occurring molecule involved in cellular energy production. NAD(P)H can exist either freely within cells or bound to proteins, and these states have different fluorescence lifetimes. The study used the proportion of protein-bound NAD(P)H as an indicator of mitochondrial metabolic activity. Because NAD(P)H occurs naturally in cells, its fluorescence provides a way to examine metabolism without introducing a fluorescent label specifically for that measurement.
The second technique, phosphorescence lifetime imaging microscopy, or PLIM, provided information about oxygen. Here the researchers used an oxygen-sensitive ruthenium-based probe. Its phosphorescence lifetime changes in response to oxygen concentration, allowing the investigators to estimate the partial pressure of oxygen, or pO2, in the brain’s vascular network. Combining FLIM and PLIM therefore provided simultaneous measurements related to cellular metabolism and vascular oxygenation.
Metabolism and oxygen differ in the Alzheimer’s model
“FLIM and PLIM simultaneous measurement requires precise synchronization between the Zeiss two-photon microscope and the Becker & Hickl lifetime-imaging electronics,” says Dr. Ammasi Periasamy, Professor and Director of the W.M. Keck Center for Cellular Imaging at UVA. “This lets us capture metabolism and oxygen tension at the same moment, in live animals. Careful calibration, together with stable physiological conditions such as body temperature and anesthesia, turns these lifetime signals into reliable oxygen measurements. It allows us to see how oxygen supply in arteries, capillaries, and veins relates to metabolic changes in the living brain.”
The measurements revealed clear differences between the two groups while the anesthetized animals were at rest. The cortices of the Alzheimer’s disease model mice showed a higher protein-bound fraction of NAD(P)H than those of wild-type animals, indicating altered mitochondrial metabolic activity.
At the same time, oxygen measurements told a related story. Oxygen partial pressure in the cortical vascular network was lower in the Alzheimer’s model than in the wild-type mice. The researchers interpret this lower vascular oxygen level as evidence of greater oxygen consumption in the Alzheimer’s disease model.
Andrés Norambuena , senior scientist at UVA and coauthor of the study remarks, “Taken together, the findings suggest that changes in cellular energy metabolism and oxygen use can be detected concurrently in the living Alzheimer’s disease mouse brain. That connection matters because mitochondrial dysfunction and impaired cerebral oxygenation have both been implicated in Alzheimer’s disease, yet they are often investigated separately.”
The work also demonstrates the value of viewing brain physiology through several measurements at once. Two-photon FLIM-PLIM can provide metabolic and oxygen information in living tissue with relatively little disruption, allowing researchers to examine relationships that are harder to resolve from isolated measurements.
The results come from a mouse model, so they do not establish that the same metabolic and oxygen patterns occur in people with Alzheimer’s disease. Instead, the study provides an imaging framework for investigating how oxygen availability and mitochondrial metabolism change together as neurological disease develops. By measuring both processes in vivo , researchers may gain a more complete view of the physiological changes that accompany Alzheimer’s disease.
For details, see the original Gold Open Access article by V. K. Sagar et al., “ Metabolism and oxygen tension in Alzheimer’s disease mouse model using two-photon FLIM-PLIM microscopy ,” Neurophotonics 13(3), 035008 (2026), doi: 10.1117/1.NPh.13.3.035008
Neurophotonics
Metabolism and oxygen tension in Alzheimer’s disease mouse model using two-photon FLIM-PLIM microscopy
11-Sep-2026