New Insights into Sugar Metabolism and Alzheimer’s Disease

Summary: Recent research suggests that sugar metabolism in brain cells plays a significant role in defending against Alzheimer’s and similar dementias. Findings show that both fly and human neurons in models of tauopathy accumulate excess glycogen, which interferes with cellular management of stress when it cannot be properly broken down.

By enhancing the enzyme glycogen phosphorylase (GlyP), researchers were able to channel sugar metabolism into a more protective route, which decreased oxidative damage and even extended the lifespan of model organisms. Interestingly, dietary restrictions and certain medications were found to boost GlyP activity, imitating this protective effect.

Key Facts:

• Glycogen Accumulation: In Alzheimer’s models, neurons build up excess glycogen, worsening damage associated with tau.
• Protective Pathway: Activating GlyP helps redirect sugar into the pentose phosphate pathway (PPP), which reduces oxidative stress in neurons.
• Therapeutic Potential: Dietary restrictions and drug treatments that mimic these restrictions can enhance brain health in both flies and human neurons.

A new study from the Buck Institute for Research on Aging highlights the important role of sugar metabolism in combating Alzheimer’s disease and related dementias.

Published in Nature Metabolism, the study reveals how breaking down glycogen, a stored form of glucose in neurons, may help protect the brain from toxic protein accumulation and degeneration.

Traditionally, glycogen has been viewed primarily as an energy reserve in liver and muscle tissues. While some glycogen is present in the brain, especially in supporting cells called astrocytes, its significance in neurons has often been overlooked.

“This novel study challenges previous beliefs and carries significant implications,” says Professor Pankaj Kapahi, a senior scientist involved in the research.

“Stored glycogen is not just inert in the brain; it’s involved in disease processes.”

Led by postdoc Sudipta Bar, PhD, the research team discovered that neurons in both fly and human tauopathy models accumulate excessive amounts of glycogen. Alarmingly, this accumulation seems to facilitate disease progression. Bar explains that tau, the protein associated with Alzheimer’s, appears to bind to glycogen, preventing its breakdown and trapping it in the process.

When glycogen remains undecomposed, neurons lose a critical mechanism needed to tackle oxidative stress—a hallmark of aging and neurodegeneration. By reactivating GlyP, which initiates glycogen breakdown, researchers demonstrated reduced tau-related damage in both fruit flies and human stem cell-derived neurons.

Instead of solely using glycogen for energy, these enzyme-activated neurons redirected the sugar to the pentose phosphate pathway. This pathway is vital for producing molecules like NADPH and Glutathione, which protect against oxidative stress.

“By boosting GlyP activity, brain cells can more effectively detoxify harmful reactive oxygen species. This not only reduces damage but can even extend the lifespan in tauopathy model flies,” Bar states.

In more encouraging news, the team showed that dietary restriction—a known method for boosting lifespan—naturally enhanced GlyP activity and led to better tau-related outcomes in flies.

They also replicated these effects using a molecule called 8-Br-cAMP, suggesting that drug activation of this sugar-clearing system might yield similar benefits.

“This study might explain why GLP-1 drugs, currently used for weight loss, show promise against dementia, possibly working similarly to dietary restriction,” Kapahi notes.

Furthermore, the same glycogen accumulation and GlyP protective effects were observed in human neurons from patients with frontotemporal dementia, supporting the potential for developing treatments.

Kapahi emphasizes the value of using fruit flies as a model in understanding how metabolic issues relate to neurodegeneration.

“Working with such a simple organism allowed us to focus on human neurons more effectively,” he adds.

He also credits the collaborative environment at the Buck Institute as a key factor in this research, drawing on expertise from various labs to address the complexities of aging and neurodegeneration.

“This study not only highlights glycogen metabolism as an unexpected ally in brain health but also paves the way for new treatment avenues for Alzheimer’s and similar diseases,” he concludes.

“As our society continues to age, findings like these provide hope that understanding and potentially balancing our brain’s sugar processes could lead to effective tools against dementia.”