Researchers at the University of Virginia developed new imaging technique to study Alzheimer's disease metabolism and oxygen use

Researchers at the University of Virginia combined two-photon fluorescence lifetime imaging microscopy with phosphorescence lifetime imaging microscopy in a study, capturing simultaneous cellular metabolism and oxygen levels in the living cerebral cortex of Alzheimer’s disease mouse models.

Alzheimer’s disease damages memory and cognition, but the condition also alters how brain tissue handles energy. Mitochondria supply much of a cell’s power, yet these structures can become dysfunctional as the disease progresses. At the same time, shifting blood flow and oxygen availability place heavy demands on cerebral tissue. A study published in Neurophotonics examines these interconnected processes together in living tissue rather than treating them as separate variables.

Dual Lifetime Microscopy

To overcome the challenge of studying metabolism and oxygen in isolation, a research group led by investigators at the University of Virginia paired two distinct imaging techniques. Measuring oxygen supply alongside cellular energy production normally proves difficult because tracking one metric fails to reveal what the other is doing.

The team used two-photon fluorescence lifetime imaging microscopy, known as FLIM, to monitor cellular metabolism without introducing artificial fluorescent labels. Instead of measuring pure brightness, FLIM tracks the duration fluorescent molecules remain in an excited state. Researchers focused on NAD(P)H, a natural molecule driving cellular energy that shifts between free and protein-bound states with distinct fluorescence lifetimes. The proportion of protein-bound NAD(P)H serves as a direct indicator of mitochondrial metabolic activity.

Simultaneously, the team deployed phosphorescence lifetime imaging microscopy, or PLIM, using an oxygen-sensitive ruthenium-based probe. Its phosphorescence lifetime shifts with oxygen concentration, allowing scientists to estimate the partial pressure of oxygen within the cerebral vascular network.

FLIM and PLIM simultaneous measurement requires precise synchronization between the Zeiss two-photon microscope and the Becker & Hickl lifetime-imaging electronics. 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.

Dr. Ammasi Periasamy, Professor and Director, via Spie

Cortical Oxygen Pressure and NAD(P)H Shifts in Alzheimer’s Models

When the researchers examined resting, anesthetized animals, the measurements exposed sharp differences between the Alzheimer’s disease mouse models and healthy wild-type mice. The cortices of the disease-model mice displayed a higher protein-bound fraction of NAD(P)H, pointing directly to altered mitochondrial metabolic activity.

Oxygen readings matched that picture. Oxygen partial pressure inside the cortical vascular network ran lower in the Alzheimer’s models than in the wild-type controls. Investigators interpret this drop in vascular oxygen as a sign of elevated oxygen consumption within the diseased brain tissue.

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.

Andrés Norambuena, senior scientist at UVA and coauthor of the study, via Spie

Spatial Metabolic Changes and Epigenetic Coupling Under Amyloid Stress

Separate investigations utilizing matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry tracked how brain energy metabolism changes with age and amyloid pathology. Those findings revealed that lactate and glutamate levels peak in young animals and decline with age, while pyruvate demonstrates the inverse trajectory. In female subjects, pyruvate-to-lactate and pyruvate-to-citrate ratios pointed toward a progressive, region-specific transition from glycolytic to oxidative metabolism.

Elevated lactate coincided with increased histone lactylation in aged females, particularly in the cortex and the CA2/CA3 hippocampal subregions. In transgenic females, lactylation concentrated tightly in putative microglia situated near amyloid plaques. While wild-type mice showed a positive correlation between lactate and histone lactylation, that relationship weakened or vanished in transgenic models, indicating that amyloid pathology disrupts the link between metabolic states and epigenetic regulation.

Establishes Framework for Tracking Mitochondrial and Oxygen Dynamics During Neurological Decline

While dual FLIM-PLIM imaging provides a less disruptive way to observe living tissue, the authors caution against immediate human extrapolation. Because data derive from animal models, the work does not confirm that identical metabolic and oxygen dynamics occur in human patients.

Instead, the study establishes an experimental framework for tracking how mitochondrial function and oxygen availability evolve alongside neurological decline. Future investigations will determine whether this simultaneous measurement technique can help characterize broader therapeutic targets.