Alzheimer’s research: French study reveals new target in the brain

A French research group has described a previously unknown mechanism that appears to play a pivotal part in the onset and progression of Alzheimer’s disease. The focus is on a specialised type of brain cell that has largely escaped attention so far - and which could, in future, become a new target for medicines.

Alzheimer’s disease: a widespread illness with no cure

Alzheimer’s is the most common form of dementia. It mainly affects people over the age of 65, and women are affected far more often than men. Those living with the condition gradually lose their memory and sense of orientation, and later often their language and personality as well.

Current estimates suggest around 900,000 people in France are living with Alzheimer’s, and about 1.8 million in Germany - and the numbers are rising as populations age. Despite extensive research and numerous drug trials, there is still no treatment that reliably halts the disease.

Clinicians and researchers have traditionally concentrated on two typical changes seen in the brain:

• Deposits of the protein beta-amyloid between nerve cells
• Clumps of the protein structure tau inside nerve cells

The so-called tau protein, in particular, is considered crucial. Under normal conditions it stabilises the internal scaffold of nerve cells. When tau regulation is disrupted, it clumps together, nerve pathways collapse, nerve cells die - and cognitive abilities decline step by step.

French team homes in on tau accumulation

This is where the newly published work by the team led by neuroendocrinologist Vincent Prévot at the Lille Neurosciences et Cognition research centre comes in. The researchers set out to understand why tau builds up so dramatically in Alzheimer’s and how this process is triggered in the first place.

"The study shows: not only nerve cells, but previously underestimated support cells in the brain control how strongly tau accumulates."

The findings were published in the specialist journal Cell Press Blue. At the centre of the work are so-called tanycytes - a cell type that many medical professionals have never even encountered.

What are tanycytes?

Tanycytes are found mainly in the hypothalamus, deep within the brain. Among other functions, this region helps regulate hormones, metabolism, temperature control, and sensations of hunger and thirst. In this location, tanycytes form a kind of interface between cerebrospinal fluid and the bloodstream.

Put simply, they carry out three key tasks:

• They transport substances from cerebrospinal fluid to specific brain regions.
• They contribute to the barrier that protects the brain from harmful substances.
• They influence which messenger substances and hormones actually reach nerve cells.

According to the team led by Prévot, they have been studying these cells for more than two decades. Their original focus was hormonal regulation. The new data now indicate that tanycytes are also directly linked to the development of Alzheimer’s.

How tanycytes influence tau in the brain (tanycytes and tau)

In their experiments, the French researchers were able to identify several steps that appear to change in people with Alzheimer’s. The full laboratory protocols remain the domain of specialist journals, but the underlying principle can be outlined as a simplified sequence:

• Tanycytes take up free tau from cerebrospinal fluid.
• In healthy brains, they break down part of this protein or pass it on in a controlled manner.
• In Alzheimer’s, this process becomes dysregulated - tanycytes are overloaded or malfunction.
• Rather than clearing tau, they contribute to the build-up of abnormal forms of the protein.
• These tau accumulations shift into vulnerable brain regions and damage nerve cells there.

"The work suggests that tanycytes are something like a ‘transfer hub’ for tau - if this system tips out of balance, a domino effect begins throughout the brain."

This brings a mechanism into focus for the first time that sits beyond the classic emphasis on nerve cells alone. That, in turn, could help explain why many therapeutic approaches aimed solely at tau inside nerve cells have produced disappointing outcomes so far.

A new target for future therapies

If tanycytes are decisive in determining whether tau accumulates, several potential therapeutic strategies come into view. Within the specialist community, three approaches are discussed most often:

• Strengthening the clearance function: Medicines could help tanycytes break down excess tau more quickly.
• Blocking faulty transport routes: If it becomes clear which channels tanycytes use to direct pathological tau into sensitive regions, these routes could be blocked in a targeted way.
• Protecting the tanycytes themselves: If the cells are damaged by inflammation or impaired blood flow, protective mechanisms or anti-inflammatory strategies may help.

All of this remains at an early stage of research. Clinical trials involving patients will only begin once the mechanisms have been clearly confirmed in animal models and cell cultures. Even so, many experts view this kind of foundational work as an important step towards moving beyond the dead ends of recent years.

Greater attention on the earliest phase of the disease

The Lille findings also reinforce another trend in international Alzheimer’s research: the focus is shifting away from late-stage disease and towards the very first changes in the brain - often decades before unmistakable memory problems appear.

Tanycytes, in particular, sit in areas closely tied to metabolism, sleep–wake rhythms and hormonal balance. Many people report years before diagnosis that they experience:

• Changes in sleep patterns
• Weight gain or weight loss without a clear cause
• Fluctuations in appetite

Whether, and in what way, these early signs are connected to altered tanycytes is still unknown. However, the study provides starting points for testing such links more systematically in future.

What patients and families can take from this

People living with Alzheimer’s and their families understandably hope above all for an effective medicine. The results presented here do not deliver a new pill, but they do shift the perspective: the spotlight moves away from the disease’s “end products” and towards the control systems behind them.

In day-to-day life, this does not translate into any immediate change. Nonetheless, the work shows that research is not simply going round in circles - it is identifying new biological pathways. The more precisely these mechanisms are mapped, the more targeted future medicines can be developed - ideally as combinations of several modes of action.

Why this kind of basic research is so demanding

Alzheimer’s is not a simple “blockage” in the brain that can be resolved with a single drug. Numerous cell types, messenger substances and metabolic pathways interact with one another. Tanycytes are only one piece of the puzzle - an underestimated one, but not the only one.

On top of that, many processes unfold gradually over years. Animal experiments can only reproduce them in part. And in the human brain, researchers are often able to intervene only very late, when the disease is already far advanced. This helps to explain why striking laboratory findings so often lose their impact in real-world settings.

Explanations of key technical terms

To keep the study in context, two brief definitions are helpful:

• Tau protein: A structural protein in nerve cells that stabilises the cell’s internal “tracks”. In its pathological form it clumps together; nerve cells lose stability and die.
• Neurodegenerative: An umbrella term for diseases in which nerve cells gradually deteriorate. This includes Alzheimer’s, Parkinson’s, and certain forms of frontotemporal dementia.

From a patient perspective, one point is particularly important: the earlier problems such as faulty tau are detected and slowed down, the longer cognitive abilities may be preserved. This is exactly where studies like the one from Lille come in - they provide the biological groundwork needed to make future early-detection and treatment strategies feasible in the first place.