Do all our cells have a type of memory, and if so, how might this influence health? We investigate.
- A
New York University study has found that kidney and nerve tissue cells can
form memories much like brain cells.
- According
to the study authors, their findings could help researchers better
understand how to treat problems that affect memory.
- They
also offer fresh insights into how human memory, as a whole, works.
- Another
recent study, from ETH Zurich in Switzerland, has found that the memories
of obesity stored in fat tissue cells may be partly responsible for the
yo-yo weight loss effect.
- This
study, conducted in mice with obesity, suggests that epigenetic changes
affecting the nucleus, or central component, of a fat cell make it more
difficult for individuals with obesity to maintain weight loss in the long
run.
Memory is one of the most
crucial aspects of our health and human identity. Through memory, we create our
individuality, our specific relationships with the world we inhabit, and we
learn to stay safe and make healthy choices.
Historically, the ability
to make, maintain, and update memories has been tied to the human brain.
Increasingly, however,
researchers are wondering if there is a whole-body memory, that is, if different parts of our
bodies can also make and store a type of memory, and if so, how these other
memories may be affected by and, in turn, impact aspects of our health.
Recently emerging evidence
seems to suggest that human memory may be an even more complex affair than we
have so far imagined.
Non-brain
cells store memories, too
In
November 2024, a team of researchers from the Center for Neural Science at New
York University (NYU) published a paper in
Speaking to Medical News Today,
lead author Nikolay Kukushkin, DPhil,
clinical associate professor of life science at NYU, told us that his “lab has
been interested in memory at its most basic level for many years.”
“In the past, we studied
sea slugs because they form very simple memories, allowing us to get to the
bottom of how they form. What we have done now is to find an even simpler
memory, which is common not just across different animals, but across all cell
types,” Kukushkin explains of his team’s new study.
“What we were hoping to
find […] is that generic cells of the body do not just have ‘memory,’ they have
memory. It’s fully literal. […] [O]ur study shows that it’s not just a
metaphorical connection — it is the same mechanism that retains information in
brain cells and in kidney cells (same cellular tools), and it follows the same
rules — namely, the spacing effect, the fact that experiences
separated in time produce a stronger memory than the same amount of experience
crammed in one go.”— Nikolay Kukushkin, DPhil
The “spacing effect” refers
to a phenomenon whereby learning, or the creation of a memory, occurs more
effectively when information, or exposure to a stimulus, is spaced out.
In their study, Kukushkin
and his team tested the formation of memories in laboratory experiments on two
types of human non-brain cells: cells collected from nerve tissue and cells
collected from kidney tissue.
They exposed both of these
types of cells to chemical signals in a spaced-out pattern mimicking the way in
which brain cells learn through exposure to such chemical information via
neurotransmitters, or chemical messengers.
The researchers found that, much like brain cells,
these other types of cells responded to the chemical signals by switching on a
gene associated with memory storage.
This suggests that, like
brain cells, other cells in the human body also accumulate memories.
What types
of memories might non-brain cells store?
The
question that then arises is: What kinds of memories might cells around the
body store? That, Kukushkin told us, “is a critical point.”
“Every system memorizes
what it experiences — a sea slug memorizes sea slug things, a human memorizes
human things, a kidney cell memorizes kidney cell things,” he explained, also
referencing previous research on
memory formation conducted on Californian sea slugs.
“We are not saying, as some
people seem to imagine, that ‘mind’ memories (emotions, knowledge, skills) are
stored in kidneys,” the researcher clarified. “Those things are still processed
in the brain, and in the brain they are stored. But other cells have their own
experiences.”
According to Kukushkin, the memories stored in
non-brain cells in other parts of the body are memories strictly related to the
roles that those specific cells play in human health.
Thus, he detailed:
“A kidney cell might be
exposed to different patterns of salts, fluids, nutrients; based on those
patterns, it might change how it acts in the future. One known example of this
kind of memory is what happens to pancreatic cells when they are exposed to a
large amount of sugar. In response, they release into the bloodstream a pulse
of insulin, a hormone that promotes sugar absorption. This pulse reaches a
certain peak, and then fades away. But wait 20 minutes and repeat the sugar
load — now the pulse of insulin becomes twice as big.”
— Nikolay Kukushkin, DPhil
“You can see why that would
be useful,” said Kukushkin, “if your sugar-absorbing capacity has been maxed
out, you should increase it to make sure you don’t waste any nutrients.”
“But if you had it
permanently increased, you’d probably be fatigued and hungry all the time. So
adding a memory element into the pancreatic cell helps it adapt to the patterns
of nutrients, just as ‘mind’ memories help us adapt to the patterns of
experience,” he hypothesized.
What
implications does body memory have for human health?
While
Kukushkin said the recent study conducted by him and his collaborators “is a
proof of principle,” other recent research more clearly shows how memories
stored in other parts of the body than the brain could affect health outcomes
in practice.
A study published in November 2024 in
The study, conducted by
researchers from ETH Zurich, in Switzerland, supports the notion that lifestyle
factors, such as unhealthy dietary patterns that can lead to chronic conditions
like obesity, can trigger
epigenetic memory formation by switching on genes that were not previously
expressed.
Ferdinand von Meyenn, PhD,
professor of nutrition and metabolic epigenetics at ETH Zurich, and one of the
lead authors of this study, told MNT that
“this project stemmed from [the team’s] curiosity about whether cells retain an
epigenetic memory of prior metabolic states.”
“Epigenetic memory is
well-known for explaining how daughter-cells maintain their transcriptional
identity through cell division, playing a vital role in development,
regeneration, and growth. But what about nondividing cells? They too must adapt
to external stimuli and therefore undergo epigenetic adaptations,” he noted.
Through this study, von
Meyenn and his colleagues wanted to figure out if a chronic condition like
obesity would change the way in which adipose tissue reacts to external factors
and, if so, if those changes were permanent or reversible.
Epigenetic
memory of obesity may hinder weight loss
“A
well-documented observation is that the body tends to defend increased body
weight, making weight loss and maintenance notoriously challenging,” von Meyenn
pointed out, referring to phenomena like yo-yo dieting, which has, in turn,
been linked to a heightened cardiovascular risk.
The researcher and his colleagues hypothesized that
“this could be due to a type of ‘metabolic memory,’ where the body remembers
and strives to return to its former state of obesity.”
To prove this hypothesis,
the researchers, in the first instance, analyzed adipose tissue from overweight
mice, as well as from mice that had shed the extra weight.
“We have found that
adipocytes carry a ‘memory’ of obesity even after significant weight loss,” von
Meyenn.
“In mouse adipocytes [fat
cells] we find that this memory is encoded in the epigenome, which are
modifications to the DNA or the proteins that the DNA is wrapped around,
controlling the activity of genes. This epigenome is changed in adipocytes of
obese mice and remains changed even after weight loss,” he went on to explain.
The second stage of the
study involved confirming the findings in humans by analyzing samples of fat
tissue from people who had undergone bariatric surgery as a form of treatment
for obesity or overweight.
“This memory seems to
prepare cells to respond quicker to an obesogenic environment [environment
conducive to wight gain] — say, high-sugar, high-fat food — which could be
linked to regain of body weight after a diet,” von Meyenn hypothesized.
“Our study indicates that
one reason why maintaining body weight after initial weight loss is difficult
is that the fat cells remember their prior obese state and likely aim to return
to this state. This means that one would have to ‘fight’ this obesogenic memory
to maintain body weight.”
— Ferdinand von Meyenn, PhD
Can the body ‘forget’ obesity?
“From
an evolutionary perspective,” said von Meyenn, maintaining a memory that
facilitates regaining, rather than shedding, weight “makes sense.”
“[H]umans and other animals
have adapted to defend their body weight rather than lose it, as food scarcity
was historically a common challenge,” the researcher explained. “On a societal
level, this could offer some solace to individuals struggling with obesity, as
it suggests that the difficulty in maintaining weight loss may not be due
solely to a lack of willpower or motivation, but rather to a deeper cellular
memory that actively resists change.”
One question remains,
however: Can such body memories of obesity be “erased” to facilitate consistent
weight loss?
This question does not, as
yet, have a straightforward answer.
“Currently, there are no pharmacological interventions
that are targeted against the epigenetic changes we have observed,” von Meyenn
told us. “Tools are being developed that could target the epigenome, but these
are very novel and have not been used in humans.”
He expressed cautious
optimism that future research will bring the answers and solutions we seek:
“It is possible that
maintaining a reduced or healthy body weight for long enough, is enough to
erase the memory. Since metabolism is intricately involved in the regulation of
the epigenome, it is also possible that certain nutritional or food supplements
could help mitigate this effect. Additionally, future studies are needed to
investigate whether incretin mimetics such as semaglutide can erase or modify
this memory.”— Ferdinand von Meyenn, PhD
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